Fix doctest for MDAnalysis.analysis.encore.similarity

[chrispfae]

Towards #3925 for MDAnalysis.analysis.encore.similarity

Changes made in this Pull Request:

• Update the docstrings in MDAnalysis.analysis.encode.similarity so that the doctests pass for this particular file

PR Checklist

• Tests?
• Docs?
• CHANGELOG updated?
• Issue raised/referenced?

[codecov]

Codecov Report

Base: 93.52% // Head: 93.53% // Increases project coverage by +0.01% 🎉

Coverage data is based on head (f5637fe) compared to base (096f799).
Patch has no changes to coverable lines.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #4021      +/-   ##
===========================================
+ Coverage    93.52%   93.53%   +0.01%     
===========================================
  Files          190      191       +1     
  Lines        25028    25063      +35     
  Branches      3542     3548       +6     
===========================================
+ Hits         23407    23443      +36     
+ Misses        1100     1099       -1     
  Partials       521      521              

Impacted Files	Coverage Δ
package/MDAnalysis/analysis/encore/similarity.py	85.62% <ø> (ø)
package/MDAnalysis/core/topology.py	98.88% <0.00%> (ø)
package/MDAnalysis/lib/_distopia.py	100.00% <0.00%> (ø)
package/MDAnalysis/auxiliary/EDR.py	98.91% <0.00%> (+0.01%)	⬆️
package/MDAnalysis/lib/distances.py	97.68% <0.00%> (+0.06%)	⬆️
package/MDAnalysis/auxiliary/base.py	92.04% <0.00%> (+0.11%)	⬆️
MDAnalysisTests/auxiliary/base.py	89.85% <0.00%> (+0.11%)	⬆️
MDAnalysisTests/coordinates/base.py	94.63% <0.00%> (+0.17%)	⬆️

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[orbeckst]

Looks pretty good, please just fix the flake8 line size that darker complains about

package/MDAnalysis/analysis/encore/similarity.py:1351:89: E501 line too long (121 > 88 characters) [flake8] 

[orbeckst]

Thank you, @chrispfae !