Build/Test Tools: Update the upgrade testing matrix to reflect 6.8.

See #63170.

git-svn-id: https://develop.svn.wordpress.org/trunk@60322 602fd350-edb4-49c9-b593-d223f7449a82

Author: desrosj

.github/workflows/upgrade-testing.yml

@@ -66,7 +66,7 @@ jobs:
         php: [ '7.2', '7.3', '7.4', '8.0', '8.1', '8.2', '8.3', '8.4' ]
         db-type: [ 'mysql' ]
         db-version: [ '5.7', '8.0', '8.4', '9.3' ]
-        wp: [ '6.6', '6.7' ]
+        wp: [ '6.7', '6.8' ]
         multisite: [ false, true ]
 
         exclude:
@@ -101,7 +101,7 @@ jobs:
         php: [ '7.2', '7.4', '8.0', '8.4' ]
         db-type: [ 'mysql' ]
         db-version: [ '5.7', '8.4' ]
-        wp: [ '6.0', '6.1', '6.2', '6.3', '6.4', '6.5' ]
+        wp: [ '6.0', '6.1', '6.2', '6.3', '6.4', '6.5', '6.6' ]
         multisite: [ false, true ]
 
         exclude: