Merge #6118: docs: add release notes notifying change of default branch to develop

8a66af2 docs: add release notes notifying change of default branch to `develop` (Kittywhiskers Van Gogh)

Pull request description:

  ## Additional Information

  Add a release note notifying the new default branch as `develop`.

  ## Checklist:

  - [x] I have performed a self-review of my own code **(note: N/A)**
  - [x] I have commented my code, particularly in hard-to-understand areas **(note: N/A)**
  - [x] I have added or updated relevant unit/integration/functional/e2e tests **(note: N/A)**
  - [x] I have made corresponding changes to the documentation
  - [x] I have assigned this pull request to a milestone _(for repository code-owners and collaborators only)_

ACKs for top commit:
  PastaPastaPasta:
    utACK 8a66af2
  UdjinM6:
    utACK 8a66af2

Tree-SHA512: 82212ce670cf4b0f243a79170914ad04b1d118406ce6402b33dfb42a5ae0865c36de4b816530238bb9ded796c66f3dcc36fa9400ace59b6e7dad24ba47653e4f

Author: PastaPastaPasta

doc/release-notes-6118.md

@@ -0,0 +1,5 @@
+Breaking Changes
+----------------
+
+* The Dash Core repository (`github.com/dashpay/dash`) will be using `develop` as its default branch. New clones
+  of the repository will no longer default to the `master` branch.