Explain we don't want MD5 checksums for versions.yml

markdown/developers/modules.md

@@ -126,6 +126,8 @@ We have implemented a number of commands in the `nf-core/tools` package to make
 
       `md5sum` checks are the preferable choice of test to determine file changes, however, this may not be possible for all outputs generated by some tools e.g. if they include time stamps or command-related headers. Please do your best to avoid just checking for the file being present e.g. it may still be possible to check that the file contains the appropriate text snippets.
 
+      > Leave the `versions.yml` entry _without_ a MD5 checksum. Indeed its content will change every time we bump the version of the software.
+
 8. Create a yaml file containing information required for module unit testing
 
    ```console