Downgrade markdown version

[andreia-ferreira]

The latest markdown versions after 0.7.3 cause the following issue to be flagged on the Google Play Console:

This PR downgrades the version and adds ignore fields in the dependabot file so that it doesn't try to update to any of the recent releases where this issue is still present

@shobhitagarwal1612 PTAL?

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 67.57%. Comparing base (68cac2d) to head (7a3de9b).

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #3859      +/-   ##
============================================
- Coverage     67.58%   67.57%   -0.01%     
+ Complexity     1853     1852       -1     
============================================
  Files           410      410              
  Lines         10818    10818              
  Branches       1425     1425              
============================================
- Hits           7311     7310       -1     
- Misses         2768     2769       +1     
  Partials        739      739              

see 1 file with indirect coverage changes

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