remove conditional rsbackend_gen import

It causes PyCharm to think methods are missing on col.backend, and
should not be needed with the move to Bazel.

pylib/anki/rsbackend.py

@@ -31,16 +31,9 @@ from anki import hooks
 from anki.dbproxy import Row as DBRow
 from anki.dbproxy import ValueForDB
 from anki.fluent_pb2 import FluentString as TR
+from anki.rsbackend_gen import RustBackendGenerated
 from anki.types import assert_impossible_literal
 
-try:
-    from anki.rsbackend_gen import RustBackendGenerated
-except ImportError:
-    # will fail during initial setup
-    class RustBackendGenerated:  # type: ignore
-        pass
-
-
 if TYPE_CHECKING:
     from anki.fluent_pb2 import FluentStringValue as TRValue