gen_gl_wrappers: remove unused imports

Fixes LGTM warnings:
    * Import of 'cProfile' is not used.
    * Import of 'pdb' is not used.
    * Import of 'string' is not used.
    * Import of 'time' is not used.

Signed-off-by: Konstantin Kharlamov <Hi-Angel@yandex.ru>
3 jobs for lgtm-fixes in 12 minutes and 22 seconds (queued for 11 seconds)
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passed #249591
debian-testing

00:01:25

 
  Build And Test
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autotools-build-and-test

00:08:50

passed #249593
meson-build-and-test

00:02:07