docs: fix link to the pull request in 42.2.3 changelog

[itchyny]

All Submissions:

• Have you followed the guidelines in our Contributing document?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?

This is a document fix.

The link of Field metadata cache can be disabled via databaseMetadataCacheFields=0 PR 1052 in https://jdbc.postgresql.org/documentation/changelog.html#version_42.2.3 is wrong. I'm not sure I can edit docs/_posts/2018-07-12-42.2.3-release.md too.

New Feature Submissions:

No

1. Does your submission pass tests?
2. Does mvn checkstyle:check pass ?

Changes to Existing Features:

No

• Does this break existing behaviour? If so please explain.
• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your core changes, as applicable?
• Have you successfully run tests with your changes locally?

[vlsi]

I'm not sure I can edit docs/_posts/2018-07-12-42.2.3-release.md too.

Please do that

[itchyny]

Thank you. I fixed the both links and rebased it.

[codecov-io]

Codecov Report

Merging #1345 into master will decrease coverage by 0.03%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master    #1345      +/-   ##
============================================
- Coverage     68.58%   68.55%   -0.04%     
+ Complexity     3883     3882       -1     
============================================
  Files           178      178              
  Lines         16205    16205              
  Branches       2646     2646              
============================================
- Hits          11114    11109       -5     
- Misses         3860     3864       +4     
- Partials       1231     1232       +1