Build/Test Tools: Properly escape $ characters in Docker compose file.

This fixes an invalid interpolation format error that can be encountered in the `mysql` container’s healthcheck test command.

Follow up to [59484].

Props afercia.
See #62221.

git-svn-id: https://develop.svn.wordpress.org/trunk@59489 602fd350-edb4-49c9-b593-d223f7449a82

docker-compose.yml

@@ -82,7 +82,7 @@ services:
     command: ${LOCAL_DB_AUTH_OPTION-}
 
     healthcheck:
-      test: [ "CMD-SHELL", "if [ \"$LOCAL_DB_TYPE\" = \"mariadb\" ]; then case \"$LOCAL_DB_VERSION\" in 5.5|10.0|10.1|10.2|10.3) mysqladmin ping -h localhost || exit $?;; *) mariadb-admin ping -h localhost || exit $?;; esac; else mysqladmin ping -h localhost || exit $?; fi" ]
+      test: [ "CMD-SHELL", "if [ \"$LOCAL_DB_TYPE\" = \"mariadb\" ]; then case \"$LOCAL_DB_VERSION\" in 5.5|10.0|10.1|10.2|10.3) mysqladmin ping -h localhost || exit $$?;; *) mariadb-admin ping -h localhost || exit $$?;; esac; else mysqladmin ping -h localhost || exit $$?; fi" ]
       timeout: 5s
       interval: 5s
       retries: 10