PR: Use notarytool instead of altool (Installers)

[mrclary]

Copied notarize.sh from master branch, but retaining DMG variable.

Description of Changes

• Wrote at least one-line docstrings (for any new functions)
• Added unit test(s) covering the changes (if testable)

• Included a screenshot or animation (if affecting the UI, see Licecap)

Just used the version of notarize.sh from master.
altool was deprecated last year, but I anticipated that we would not be developing on 5.x for this long, so I did not update to notarytool. The notarizing on master has always used notarytool.

Issue(s) Resolved

Fixes #21951

Affirmation

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[dalthviz]

Thanks @mrclary ! From my understanding things look good here 👍, but just in case, is there anything else pending to do before merging this?

[mrclary]

It should be good to go. Thanks @dalthviz .

[ccordoba12]

Thanks @mrclary!