Fix TypeError: '>=' not supported between instances of 'str' and 'int' in msvs_emulation.py

[critical-bug]

Fixes a mere syntax problem.

When I build mozc, GYP gives the following error:

Traceback (most recent call last):
  File "C:\work\depot_tools\bootstrap-2@3_8_9_chromium_14_bin\python3\bin\lib\multiprocessing\pool.py", line 125, in worker
    result = (True, func(*args, **kwds))
  File "C:\work\depot_tools\bootstrap-2@3_8_9_chromium_14_bin\python3\bin\lib\multiprocessing\pool.py", line 48, in mapstar
    return list(map(*args))
  File "C:\work\mozc\src\third_party\gyp\pylib\gyp\generator\ninja.py", line 2467, in CallGenerateOutputForConfig
    GenerateOutputForConfig(target_list, target_dicts, data, params, config_name)
  File "C:\work\mozc\src\third_party\gyp\pylib\gyp\generator\ninja.py", line 2405, in GenerateOutputForConfig
    target = writer.WriteSpec(spec, config_name, generator_flags)
  File "C:\work\mozc\src\third_party\gyp\pylib\gyp\generator\ninja.py", line 484, in WriteSpec
    link_deps = self.WriteSources(
  File "C:\work\mozc\src\third_party\gyp\pylib\gyp\generator\ninja.py", line 923, in WriteSources
    return self.WriteSourcesForArch(
  File "C:\work\mozc\src\third_party\gyp\pylib\gyp\generator\ninja.py", line 946, in WriteSourcesForArch
    asmflags = self.msvs_settings.GetAsmflags(config_name)
  File "C:\work\mozc\src\third_party\gyp\pylib\gyp\msvs_emulation.py", line 436, in GetAsmflags
    config = self._TargetConfig(config)
  File "C:\work\mozc\src\third_party\gyp\pylib\gyp\msvs_emulation.py", line 324, in _TargetConfig
    if self.vs_version.short_name >= 2015:
TypeError: '>=' not supported between instances of 'str' and 'int'

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