Remove warning about unspecified environment

Currently if not target platform environment is specified Tycho emits a
warning "No explicit target runtime environment configuration. Build is
platform dependent." beside from that nothing ever seems go wrong and
actually Tycho builds *can* be environment agnostic. Also there is not
really a way to tell Tycho that it is okay, so either the user has to
use a specific one or configure many ones that make resolving slower.

This now removes this warning, if with modern Tycho there are any
problems that arise from a missing environment configuration one should
better give a specific error/hint at this place instead of warn "just in
case".

(cherry picked from commit 8395720)

tycho-core/src/main/java/org/eclipse/tycho/core/resolver/DefaultTargetPlatformConfigurationReader.java

@@ -167,8 +167,6 @@ public TargetPlatformConfiguration getTargetPlatformConfiguration(MavenSession s
         }
 
         if (result.getEnvironments().isEmpty()) {
-            // applying defaults
-            logger.warn("No explicit target runtime environment configuration. Build is platform dependent.");
             result.addEnvironment(TargetEnvironment.getRunningEnvironment());
             result.setImplicitTargetEnvironment(true);
         } else {