Update openjdk Docker tag to v8

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
openjdk	final	patch	8u252-slim -> 8-slim

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[codecov]

Codecov Report

Merging #1013 into master will increase coverage by 0.04%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1013      +/-   ##
==========================================
+ Coverage   85.23%   85.28%   +0.04%     
==========================================
  Files         221      221              
  Lines        4444     4444              
  Branches      301      301              
==========================================
+ Hits         3788     3790       +2     
  Misses        564      564              
+ Partials       92       90       -2     

[renovate]

Autoclosing Skipped

This PR has been flagged for autoclosing, however it is being skipped due to the branch being already modified. Please close/delete it manually or report a bug if you think this is in error.