Update the documents to be up-to-date with new undo command

[aidoxe-123]

No description provided.

[codecov-io]

Codecov Report

Merging #131 into master will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master     #131   +/-   ##
=========================================
  Coverage     74.95%   74.95%           
  Complexity      520      520           
=========================================
  Files            84       84           
  Lines          1705     1705           
  Branches        134      134           
=========================================
  Hits           1278     1278           
  Misses          377      377           
  Partials         50       50           

Impacted Files	Coverage Δ	Complexity Δ
...java/jimmy/mcgymmy/logic/commands/UndoCommand.java	100.00% <ø> (ø)	3.00 <0.00> (ø)

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[Jh123x]

LGTM