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>
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