Update to match FluentKit's declared version minimums

[gwynne]

This should help fix building in Xcode.

[codecov-commenter]

Codecov Report

Merging #204 (731b5f7) into main (44247df) will not change coverage.
The diff coverage is n/a.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #204   +/-   ##
=======================================
  Coverage   77.29%   77.29%           
=======================================
  Files           7        7           
  Lines         414      414           
=======================================
  Hits          320      320           
  Misses         94       94           

Impacted Files	Coverage Δ
...ntPostgresDriver/FluentPostgresConfiguration.swift	43.47% <ø> (ø)
.../FluentPostgresDriver/FluentPostgresDatabase.swift	88.11% <ø> (ø)
...es/FluentPostgresDriver/FluentPostgresDriver.swift	81.25% <ø> (ø)
.../FluentPostgresDriver/PostgresError+Database.swift	86.11% <ø> (ø)
...es/FluentPostgresDriver/PostgresRow+Database.swift	88.88% <ø> (ø)

[gwynne]

Exports test won't pass until a PostgresKit release has been tagged

[VaporBot]

These changes are now available in 2.5.1