docs: Remove arm64 section and add PR push auth solution (#498)

* docs: Remove arm64 section and add PR push auth solution

Enabling the arm64 plugin will break Tutor in latest version. Keep it disabled even on M1 machines.

* Refer to gh documentation

source/developers/quickstarts/first_openedx_pr.rst

@@ -106,15 +106,6 @@ version of the code (as opposed to the most recent named release):
   git clone --branch=nightly https://github.com/overhangio/tutor.git
   pip install -e "./tutor[full]"
 
-If you are using ARM-64 (such as a MacBook M1 or M2), then install this extra plugin and enable it
-(if you're not, then skip this step):
-
-.. code-block:: bash
-
-  pip install git+https://github.com/open-craft/tutor-contrib-arm64
-  tutor plugins enable arm64
-  tutor config save
-
 Finally, let's configure and provision your Open edX instance!
 You will be asked a couple questions.
 Answer them however you like, although the default answers will work fine.
@@ -266,6 +257,13 @@ Now push your changes to a new branch in your fork::
 
     git push --set-upstream origin developer_quickstart
 
+If you get a ``fatal: Authentication failed`` error, authenticate Git Hub by running::
+
+   gh auth login
+
+Learn more about authentication `here <https://docs.github.com/en/authentication/keeping-your-account-and-data-secure/about-authentication-to-github#about-authentication-to-github>`_.
+
+
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