remove flag from version filter

[vvcephei]

Remove the default-disabled feature flag from the version-filter patch.

The flag was added in case the patch didn't work as expected, but
in that case, users can always just fall back to a vanilla release of
Maven.

I think there are two good reasons to just enable the patch unconditionally:

1. As is, having this flag makes it difficult to use, since you always
   have to remember the flag, and if you forget, you're in for a couple of hours
   of downloading pom files.
2. Just patching the binary lets us swap out the Maven binary in IDEA as well,
   which means we get the benefit of this patch while resolving dependencies
   in the IDE. In contrast, there's no way to supply a flag to be used with the
   maven wrapper in a way that all IDE operations avoid downloading the
   unnecessary older versions.

[vvcephei]

Hey @xli1996 , what do you think about removing the feature flag? My reasoning is above.

If you want to accept this patch, I think we'll also have to bump the versions in this repo, but I wanted to run it by you first.

[vvcephei]

To test this patch:

I built it:

 mvn -DdistributionTargetDir="$HOME/maven-custom/" clean package

Then, I cleaned up my env:

cd ksql
mvn clean
rm -r ~/.m2/repository
~/maven-custom/bin/mvn clean compile

I visually verified that only the latest versions get resolved, and also the build takes about 12 minutes, while it would otherwise take hours.

I also tested this in IDEA by setting Settings > Build,Execution,Deployment > Build Tools > Maven > Maven home path to /home/john/maven-custom. Then, I deleted the ksql project, cleared caches, did another mvn clean and another rm -r ~/.m2/repository. Upon importing the ksql project again, I observed that it does have to resolve all artifacts, but it only resolves the latest ones, and again the whole import takes about 12 minutes.