Fix link to rtm.connect docs

[sampart]

Summary

Fix link to rtm.connect docs in docs-src/real_time_messaging.rst

Requirements (place an x in each [ ])

• I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.

[codecov]

Codecov Report

Merging #223 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #223   +/-   ##
=======================================
  Coverage   59.67%   59.67%           
=======================================
  Files           9        9           
  Lines         310      310           
  Branches       57       57           
=======================================
  Hits          185      185           
  Misses        111      111           
  Partials       14       14

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[Roach]

@sampart can you merge master and run tox -e docs on this branch? I'll get it merged in as soon as the docs are regenerated 👍

[sampart]

@Roach do you definitely want a merge, or could I rebase off master? I'd rather not have an unnecessary merge commit. Thanks

[Roach]

@sampart I'm fine with either, whichever works for you 👍

[sampart]

@Roach I've rebased the branch and amended the commit to include the generated docs too. Let me know if you need anything more from me. Thanks