Ensure Pipeline graph does not share axes with other plots

[philippjfr]

Fixes #1276

[codecov]

Codecov Report

Merging #1438 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1438   +/-   ##
=======================================
  Coverage   87.90%   87.90%           
=======================================
  Files         135      135           
  Lines       14879    14879           
=======================================
  Hits        13079    13079           
  Misses       1800     1800           

Impacted Files	Coverage Δ
panel/pipeline.py	88.57% <ø> (ø)

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