docs: Remove traces of AB3 from README

[taufiq]

This commit removes the traces of AB3 in README that was pointed out in the cs2103 tracker.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 73.93%. Comparing base (7c90816) to head (6eda9ad).

Additional details and impacted files

@@            Coverage Diff            @@
##             master      #33   +/-   ##
=========================================
  Coverage     73.93%   73.93%           
  Complexity      419      419           
=========================================
  Files            75       75           
  Lines          1362     1362           
  Branches        126      126           
=========================================
  Hits           1007     1007           
  Misses          325      325           
  Partials         30       30           

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[yadunut]

LGTM!

[taufiq]

Sui

[AdityaB4]

We might need to remove the reference to AB3 in the acknowledgement as well, we can come back to this if the tracker does not update still.

[blaukc]

We might need to remove the reference to AB3 in the acknowledgement as well, we can come back to this if the tracker does not update still.

The other groups did the same I think