Remove Duplicates from Releases Importer

What does this MR do and why?

Modifies the GitHub ReleasesImporter to strip out and ignore any incoming releases with null tags

Screenshots or screen recordings

[18] pry(main)> p
=> #<Project id:49 root/test2>>
[19] pry(main)> p_orig.releases.count
   (0.4ms)  SELECT COUNT(*) FROM "releases" WHERE "releases"."project_id" = 48 /*application:console,db_config_name:main,line:(pry):19:in `__pry__'*/
=> 2

After importing the test project with a null tag release, the release has been stripped out

=> #<Project id:49 root/test2>>
[14] pry(main)> p.releases.count
   (0.5ms)  SELECT COUNT(*) FROM "releases" WHERE "releases"."project_id" = 49 /*application:console,db_config_name:main,line:(pry):14:in `__pry__'*/
=> 1

How to set up and validate locally

2022-01-24_13-20-708_root_test_export.tar.gz

1. Import the test project that has two releases, one release with a null tag
2. Check the new project releases page, it should only have one release
3. Use the rails console to check that the new project only has one release

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.