Merge pull request #763 from humanmade/417-clarify-php-versions

Clarify how PHP versions are specified.

docs/php-version.md

@@ -19,6 +19,9 @@ To change the PHP version use the Local Server module configuration to set the `
 }
 ```
 
+**Note**: Only the major and minor versions (x.y) should be specified. Altis automatically manages and updates the patch version
+as part of regular maintenance.
+
 Altis will always default to the _highest_ supported version of PHP unless support is marked as
 experimental. [See the PHP compatibility chart here](docs://guides/updating-php/README.md) to see which version of PHP your version
 of Local Server will be running on by default, and which other versions are available.