fix two validate database checks that never ran

[dereklichtner]

Two checks in GeMS_ValidateDatabase.py never actually ran. Checks would always pass even if dataset was not correct.

compare_sr() meant to flag when two feature classes use different spatial references but it was reading both spatial refs from the first feature class:

sr1 = db_dict[obj1]["spatialReference"].name
sr2 = db_dict[obj1]["spatialReference"].name   # should be obj2

So it always compared a feature class to itself and never reported a mismatch.

Also, metadata check used Path(metadata_file).exists ie the method itself. "Does not exist" branch would never run and validate_w_mp() was passed missing file. Now calls .exists() with parentheses

Verified with ArcGIS Pro 3.6.1 with WSGS GeMS gdbs.

The affected lines are the same on master and Version-3.