Build/Test Tools: Fix 2 matrix errors in the 5.7 branch.

These are caused by an empty split_slow value when one is always expected.

Follow up to [58598].

See #61213.

git-svn-id: https://develop.svn.wordpress.org/branches/5.7@58604 602fd350-edb4-49c9-b593-d223f7449a82

Author: desrosj

.github/workflows/phpunit-tests.yml

@@ -64,24 +64,19 @@ jobs:
             os: ubuntu-latest
             memcached: true
             multisite: false
+            split_slow: false
           - php: '7.4'
             os: ubuntu-latest
             memcached: true
             multisite: true
-          # Report the results of the PHP 7.4 without memcached job.
-          - php: '7.4'
-            os: ubuntu-latest
-            memcached: false
-            multisite: false
-            report: true
+            split_slow: false
     with:
       os: ${{ matrix.os }}
       php: ${{ matrix.php }}
       multisite: ${{ matrix.multisite }}
       split_slow: ${{ matrix.split_slow }}
       memcached: ${{ matrix.memcached }}
       phpunit-config: ${{ matrix.multisite && 'tests/phpunit/multisite.xml' || 'phpunit.xml.dist' }}
-      report: ${{ matrix.report || false }}
 
   slack-notifications:
     name: Slack Notifications