Remove Beta label from some Spark tools

[tomwhite]

Now that Disq runs tests on 'large' BAM and VCF files (disq-bio/disq#103), we can remove the Beta label from some more of the Spark tools.

[codecov]

Codecov Report

Merging #5991 into master will increase coverage by 0.001%.
The diff coverage is n/a.

@@               Coverage Diff               @@
##              master     #5991       +/-   ##
===============================================
+ Coverage     86.926%   86.927%   +0.001%     
+ Complexity     32732     32731        -1     
===============================================
  Files           2014      2014               
  Lines         151333    151333               
  Branches       16612     16612               
===============================================
+ Hits          131548    131549        +1     
  Misses         13724     13724               
+ Partials        6061      6060        -1

Impacted Files	Coverage Δ	Complexity Δ
...lbender/tools/spark/pipelines/CountReadsSpark.java	90.909% <ø> (ø)	5 <0> (ø)	⬇️
...ellbender/tools/spark/pipelines/FlagStatSpark.java	90% <ø> (ø)	4 <0> (ø)	⬇️
...lbender/tools/spark/pipelines/CountBasesSpark.java	90% <ø> (ø)	5 <0> (ø)	⬇️
...nder/tools/spark/pipelines/PrintVariantsSpark.java	66.667% <ø> (ø)	2 <0> (ø)	⬇️
...nder/tools/spark/pipelines/CountVariantsSpark.java	90.909% <ø> (ø)	4 <0> (ø)	⬇️
...lbender/tools/spark/pipelines/PrintReadsSpark.java	100% <ø> (ø)	3 <0> (ø)	⬇️
...lotypecaller/readthreading/ReadThreadingGraph.java	88.971% <0%> (+0.245%)	159% <0%> (ø)	⬇️

[tomwhite]

@droazen I checked and PrintReadsSparkIntegrationTest and PrintVariantsSparkIntegrationTest both test GCS inputs and outputs, so it should be OK to take PrintReadsSpark and PrintVariantsSpark out of beta too.

[jamesemery]

After some discussion we have decided that removing beta tags from these tools is certainly no more dangerous than it was for MarkDuplicatesSpark, especially given recent fixes in Disq we can be at least a little more confident that spark can handle at least some of our regular use cases.