Don't plan twice

I got following error when testing.

```
% prove t/style-no-tabs.t
t/style-no-tabs.t .. You tried to plan twice at t/style-no-tabs.t line 18.
# Looks like your test exited with 2 before it could output anything.
t/style-no-tabs.t .. Dubious, test returned 2 (wstat 512, 0x200)
No subtests run 

Test Summary Report
-------------------
t/style-no-tabs.t (Wstat: 512 Tests: 0 Failed: 0)
  Non-zero exit status: 2
  Parse errors: No plan found in TAP output
Files=1, Tests=0,  0 wallclock secs ( 0.02 usr  0.01 sys +  0.02 cusr  0.01 csys =  0.06 CPU)
Result: FAIL

```