Merge branch 'cs/zend-test-braces-fixes'
removed unused variable , removed else block
added docblock comment
#6919 - add `SqlInterface#getSqlString()` return value signature
#6919 - fixed `Sql#getSqlStringForSqlObject()` return value
Merge branch 'cs/#6919-remove-unused-zend-db-sql-sql-variable' into develop

Close #6919
Forward port #6919