MINOR: Remove reference to docker image that is no longer available

[andygrove]

Which issue does this PR close?

N/A

Rationale for this change

Documentation refers to ballistacompute/spark-benchmarks:0.4.0-SNAPSHOT image that no longer exists.

What changes are included in this PR?

Remove some docs.

Are there any user-facing changes?

No

[codecov-commenter]

Codecov Report

Merging #2795 (4ce148f) into master (7c60412) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #2795   +/-   ##
=======================================
  Coverage   85.14%   85.14%           
=======================================
  Files         273      273           
  Lines       48248    48248           
=======================================
  Hits        41079    41079           
  Misses       7169     7169           

Impacted Files	Coverage Δ
datafusion/expr/src/logical_plan/plan.rs	73.91% <0.00%> (ø)

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