extensions: remove 'check_env' method

The method is not documented or used.
It was introduced for quota but unused since commit 603e3b78.

Closes-Bug: #1328362
Change-Id: Id0a4d8606f34e54468ed0de26adbf25ff273079e
Imported Translations from Transifex

Change-Id: Ib6b1eb8816862ba17c40d7fb0a510e1936503ec4
Merge "Imported Translations from Transifex"
Merge "extensions: remove 'check_env' method"