Reduce dependency conflicts

[gesellix]

Relates to #3308

Naïve dependency enforcement leads to a failing build:

Execution failed for task ':testcontainers:japicmp'.
> Could not resolve all dependencies for configuration ':testcontainers:baseline'.
   > Conflict(s) found for the following module(s):
       - org.testcontainers:testcontainers between versions 1.15.1 and unspecified
     Run with:
         --scan or
         :testcontainers:dependencyInsight --configuration baseline --dependency org.testcontainers:testcontainers
     to get more insight on how to solve the conflict.