Fix dangerous commands validation

コマンド内に s/ があると誤爆していたので修正してみました。
自分のvimrcだと以下のコマンド等々で引っかかってます。
```
runtime macros/matchit.vim
```

修正後に簡単に動作確認してみた結果です。
```
$ cat s.vim 
s///
su///
sub///
subs///
subst///
substi///
substit///
substitu///
substitut///
substitute///
&
&&
~
~&
~g&
sno
snom
snoma
snomag
snomagi
snomagic
sm
sma
smag
smagi
smagic
a s/
a &
a ~
$ vint s.vim
s.vim:1:1: Avoid commands that rely on user settings (see Google VimScript Style Guide (Fragile))
s.vim:1:1: Do not use the command that has unintended side effect (see Google VimScript Style Guide (Dangerous))
s.vim:2:1: Avoid commands that rely on user settings (see Google VimScript Style Guide (Fragile))
s.vim:2:1: Do not use the command that has unintended side effect (see Google VimScript Style Guide (Dangerous))
s.vim:3:1: Do not use the command that has unintended side effect (see Google VimScript Style Guide (Dangerous))
s.vim:4:1: Avoid commands that rely on user settings (see Google VimScript Style Guide (Fragile))
s.vim:4:1: Do not use the command that has unintended side effect (see Google VimScript Style Guide (Dangerous))
s.vim:5:1: Do not use the command that has unintended side effect (see Google VimScript Style Guide (Dangerous))
s.vim:6:1: Do not use the command that has unintended side effect (see Google VimScript Style Guide (Dangerous))
s.vim:7:1: Do not use the command that has unintended side effect (see Google VimScript Style Guide (Dangerous))
s.vim:8:1: Do not use the command that has unintended side effect (see Google VimScript Style Guide (Dangerous))
s.vim:9:1: Do not use the command that has unintended side effect (see Google VimScript Style Guide (Dangerous))
s.vim:10:1: Avoid commands that rely on user settings (see Google VimScript Style Guide (Fragile))
s.vim:10:1: Do not use the command that has unintended side effect (see Google VimScript Style Guide (Dangerous))
s.vim:11:1: Do not use the command that has unintended side effect (see Google VimScript Style Guide (Dangerous))
s.vim:12:1: Do not use the command that has unintended side effect (see Google VimScript Style Guide (Dangerous))
s.vim:13:1: Do not use the command that has unintended side effect (see Google VimScript Style Guide (Dangerous))
s.vim:14:1: Do not use the command that has unintended side effect (see Google VimScript Style Guide (Dangerous))
s.vim:15:1: Do not use the command that has unintended side effect (see Google VimScript Style Guide (Dangerous))
s.vim:16:1: Do not use the command that has unintended side effect (see Google VimScript Style Guide (Dangerous))
s.vim:17:1: Do not use the command that has unintended side effect (see Google VimScript Style Guide (Dangerous))
s.vim:18:1: Do not use the command that has unintended side effect (see Google VimScript Style Guide (Dangerous))
s.vim:19:1: Do not use the command that has unintended side effect (see Google VimScript Style Guide (Dangerous))
s.vim:20:1: Do not use the command that has unintended side effect (see Google VimScript Style Guide (Dangerous))
s.vim:21:1: Do not use the command that has unintended side effect (see Google VimScript Style Guide (Dangerous))
s.vim:22:1: Do not use the command that has unintended side effect (see Google VimScript Style Guide (Dangerous))
s.vim:23:1: Do not use the command that has unintended side effect (see Google VimScript Style Guide (Dangerous))
s.vim:24:1: Do not use the command that has unintended side effect (see Google VimScript Style Guide (Dangerous))
s.vim:25:1: Do not use the command that has unintended side effect (see Google VimScript Style Guide (Dangerous))
s.vim:26:1: Do not use the command that has unintended side effect (see Google VimScript Style Guide (Dangerous))
s.vim:27:1: Avoid commands that rely on user settings (see Google VimScript Style Guide (Fragile))
$ 
```