Remove Ballista CI check

[andygrove]

Which issue does this PR close?

Closes #2679

Rationale for this change

See #2679

What changes are included in this PR?

• Remove Ballista CI check
• Update PR template

Are there any user-facing changes?

No

Does this PR break compatibility with Ballista?

We will never know

[codecov-commenter]

Codecov Report

Merging #2684 (4998667) into master (49e072a) will increase coverage by 0.06%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #2684      +/-   ##
==========================================
+ Coverage   84.63%   84.69%   +0.06%     
==========================================
  Files         267      267              
  Lines       46867    47004     +137     
==========================================
+ Hits        39665    39811     +146     
+ Misses       7202     7193       -9     

Impacted Files	Coverage Δ
...afusion/core/src/datasource/file_format/parquet.rs	87.32% <0.00%> (-1.24%)	⬇️
datafusion/core/src/physical_plan/metrics/value.rs	86.93% <0.00%> (-0.51%)	⬇️
datafusion/common/src/scalar.rs	74.94% <0.00%> (-0.24%)	⬇️
...sion/core/src/physical_plan/file_format/parquet.rs	95.21% <0.00%> (-0.02%)	⬇️
datafusion/core/tests/parquet_pruning.rs	98.36% <0.00%> (-0.01%)	⬇️
datafusion/core/tests/sql/parquet.rs	100.00% <0.00%> (ø)
datafusion/expr/src/utils.rs	91.86% <0.00%> (+0.07%)	⬆️
datafusion/sql/src/planner.rs	81.60% <0.00%> (+0.13%)	⬆️
datafusion/core/src/optimizer/filter_push_down.rs	98.14% <0.00%> (+0.58%)	⬆️
datafusion/expr/src/logical_plan/plan.rs	68.15% <0.00%> (+0.96%)	⬆️
... and 1 more

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[alamb]

Thank you @andygrove and @tustvold