Use pull_request_target trigger in release workflow

[epassaro]

Description

The new release workflow is not triggered automatically after merging the changes from pre-release.

This happens because I used the wrong trigger: pull_request does not have access to the required BOT_TOKEN to make this operation.

We need to use pull_request_target for that as it was described in the GitHub Documentation.

The manual workflow_dispatch trigger seems to work just right.

Motivation and context

How has this been tested?

• Testing pipeline
• Other

Examples

Type of change

• Bug fix
• New feature
• Breaking change
• None of the above

Checklist

• I have updated the documentation according to my changes
• I have built the documentation by applying the build_docs label to this pull request (if you don't have enough privileges a reviewer will do it for you)
• I have requested two reviewers for this pull request

[codecov]

Codecov Report

Merging #2007 (fd42b3a) into master (1133636) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #2007   +/-   ##
=======================================
  Coverage   59.99%   59.99%           
=======================================
  Files          70       70           
  Lines        8112     8112           
=======================================
  Hits         4867     4867           
  Misses       3245     3245           

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