PG-464: Update regression status badges links.

[Naeem-Akhter]

As per discussion in the team meeting, removed status badges for Pg-11~13 jobs from README. We should only be displaying the status badges for the latest PG version (GA) and code coverage.

[codecov[bot]]

Codecov Report

Merging #293 (141f1c0) into main (63bc740) will increase coverage by 0.31%. The diff coverage is n/a.

@@            Coverage Diff             @@
##             main     #293      +/-   ##
==========================================
+ Coverage   88.87%   89.19%   +0.31%     
==========================================
  Files           3        3              
  Lines        1285     1286       +1     
  Branches       47       47              
==========================================
+ Hits         1142     1147       +5     
+ Misses        119      116       -3     
+ Partials       24       23       -1     

Impacted Files	Coverage Δ
pg_stat_monitor.c	89.44% <0.00%> (+0.37%)	:arrow_up:

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