Adds support for Elasticsearch 7.9.1 and updates release notes

[dbbaughe]

Issue #, if available:

Description of changes:
Adds support for ES 7.9.1
This will fail while waiting for notification jar to be published to maven

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov]

Codecov Report

Merging #288 into master will decrease coverage by 0.02%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master     #288      +/-   ##
============================================
- Coverage     75.22%   75.19%   -0.03%     
  Complexity      703      703              
============================================
  Files            89       89              
  Lines          3919     3919              
  Branches        625      625              
============================================
- Hits           2948     2947       -1     
  Misses          643      643              
- Partials        328      329       +1     

Impacted Files	Coverage Δ	Complexity Δ
...anagement/indexstatemanagement/model/Transition.kt	80.39% <0.00%> (-1.97%)	5.00% <0.00%> (ø%)

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