git.install: Do not specify /CLOSEAPPLICATIONS /RESTARTAPPLICATIONS

There is not need to specify these as this is Inno Setup's default
behavior anyway [1] [2]. Moreover, upcoming Git for Windows releases will
disable Inno Setup's built-in RestartManager in favor of a custom one that
is able to detect locking processes also prior to Windows Vista.

[1] http://www.jrsoftware.org/ishelp/index.php?topic=setup_closeapplications
[2] http://www.jrsoftware.org/ishelp/index.php?topic=setup_restartapplications