Build/Test Tools: Remove version from docker-compose.yml.

The `version` property throws a warning when working with the local Docker environment. According to the Docker Compose spec, the property only remains for backward compatibility and should be removed.

Props narenin, mukesh27, swissspidy.
Fixes #61101.

git-svn-id: https://develop.svn.wordpress.org/trunk@58157 602fd350-edb4-49c9-b593-d223f7449a82

docker-compose.yml

@@ -1,5 +1,3 @@
-version: '3.7'
-
 services:
 
   ##