Fixed the logic for checking source db version compatibility and added it to assess migration too for PG

[ShivanshGahlot]

Describe the changes in this pull request

There was a bug in the logic for checking if source db version is compatibily in PG. Even with 16.2 source db version and max allowed version 16, it was failing. Fixed the logic to check only the major version.

Describe if there are any user-facing changes

None

How was this pull request tested?

Manually tested

Does your PR have changes that can cause upgrade issues?

Component	Breaking changes?
MetaDB	No
Name registry json	No
Data File Descriptor Json	No
Export Snapshot Status Json	No
Import Data State	No
Export Status Json	No
Data .sql files of tables	No
Export and import data queue	No
Schema Dump	No
AssessmentDB	No
Sizing DB	No
Migration Assessment Report Json	No
Callhome Json	No
YugabyteD Tables	No
TargetDB Metadata Tables	No

[priyanshi-yb]

LGTM!