Fix PR link format for 1.13.0.0 release notes

[qreshi]

Issue #, if available:

Description of changes:

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 #345 (1f19445) into master (3ac912d) will increase coverage by 0.15%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master     #345      +/-   ##
============================================
+ Coverage     79.16%   79.31%   +0.15%     
- Complexity      200      202       +2     
============================================
  Files           151      151              
  Lines          5323     5323              
  Branches        698      698              
============================================
+ Hits           4214     4222       +8     
+ Misses          738      727      -11     
- Partials        371      374       +3     

Impacted Files	Coverage Δ	Complexity Δ
...ing/destination/client/DestinationEmailClient.java	72.50% <0.00%> (-5.00%)	7.00% <0.00%> (-1.00%)
...e/action/node/ScheduledJobsStatsTransportAction.kt	75.00% <0.00%> (ø)	8.00% <0.00%> (ø%)
...asticsearch/alerting/core/schedule/JobScheduler.kt	75.71% <0.00%> (+4.28%)	15.00% <0.00%> (ø%)
...rch/alerting/core/action/node/ScheduledJobStats.kt	66.66% <0.00%> (+11.11%)	4.00% <0.00%> (+1.00%)
...arch/alerting/core/schedule/JobSchedulerMetrics.kt	76.47% <0.00%> (+17.64%)	6.00% <0.00%> (+2.00%)

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