pgsql: Improve logic in PostgresVersion.pm

Improve logic in PostgresVersion.pm

Handle the situation where perl swaps the order of operands of
the comparison operator. See `perldoc overload` for details:

The third argument is set to TRUE if (and only if) the two
operands have been swapped. Perl may do this to ensure that the
first argument ($self) is an object implementing the overloaded
operation, in line with general object calling conventions.

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/fa26eba221a9e837493df47d0255ce615129e9a8

Modified Files
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src/test/perl/PostgresVersion.pm | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)