Adds missing timestep equality tests

[IAlibay]

Fixes #3329

Changes made in this Pull Request:

• Adds a couple extra tests for ts.__eq__ coverage

PR Checklist

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

[codecov]

Codecov Report

Merging #3388 (9024167) into develop (f8bb8ec) will increase coverage by 0.01%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           develop    #3388      +/-   ##
===========================================
+ Coverage    93.65%   93.66%   +0.01%     
===========================================
  Files          177      177              
  Lines        22869    22869              
  Branches      3229     3229              
===========================================
+ Hits         21417    21421       +4     
+ Misses        1401     1397       -4     
  Partials        51       51              

Impacted Files	Coverage Δ
package/MDAnalysis/coordinates/base.py	95.35% <0.00%> (+0.47%)	⬆️

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