[ticket/12940] Remove unused use statements.

PHPBB3-12940
Merge pull request #2843 from bantu/ticket/12940

[ticket/12940] Remove unused use statements.
Merge branch 'develop-ascraeus' into develop

# By Andreas Fischer
# Via Andreas Fischer (1) and Dhruv Goel (1)
* develop-ascraeus:
  [ticket/12940] Remove unused use statements.