deps: bump Spanner to 6.25.5

[olavloite]

Bumps the Spanner version to 6.25.5 and updates other dependencies to
the most recent versions. Also adds the most recent patch versions to
the list of PG JDBC versions that we test.

[codecov]

Codecov Report

Merging #172 (41d30f9) into postgresql-dialect (1f0ab3a) will increase coverage by 0.21%.
The diff coverage is n/a.

@@                   Coverage Diff                    @@
##             postgresql-dialect     #172      +/-   ##
========================================================
+ Coverage                 77.64%   77.85%   +0.21%     
- Complexity                  958      959       +1     
========================================================
  Files                        85       85              
  Lines                      3283     3283              
  Branches                    384      384              
========================================================
+ Hits                       2549     2556       +7     
+ Misses                      578      572       -6     
+ Partials                    156      155       -1     

Flag	Coverage Δ
all_tests	77.85% <ø> (+0.21%)	⬆️

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Impacted Files	Coverage Δ
...gle/cloud/spanner/pgadapter/ConnectionHandler.java	76.19% <0.00%> (+3.33%)	⬆️

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