src: remove unused file variable.

Currently the following compiler warning is displayed:

../src/module_wrap.cc:330:3: warning: unused variable 'file_check'
[-Wunused-variable]
} file_check;
  ^

This commit removes this unused variable.

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• commit message follows commit guidelines

Affected core subsystem(s)

src