chore: removing send mail on failure gh action

This action frequently fails, and the current maintainers
(@openedx/2U-aperture) don't require it, as we both monitor the success
of the workflows and we have workflow failure email notifications
enabled. After discussion with Axim, we are removing the  action. It can
always be added back (and potentially debugged) later if another
maintainer would benefit from it.

FIXES: APER-3814

.github/workflows/ci.yml

@@ -41,20 +41,3 @@ jobs:
       with:
         token: ${{ secrets.CODECOV_TOKEN }}
         fail_ci_if_error: true
-
-    - name: Send failure notification
-      if: ${{ failure() }}
-      uses: dawidd6/action-send-mail@v4
-      with:
-        server_address: email-smtp.us-east-1.amazonaws.com
-        server_port: 465
-        username: ${{ secrets.EDX_SMTP_USERNAME }}
-        password: ${{ secrets.EDX_SMTP_PASSWORD }}
-        subject: CI workflow failed in ${{github.repository}}
-        to: masters-grades@edx.org,aperture@2u-internal.opsgenie.net
-        from: github-actions <github-actions@edx.org>
-        nodemailerlog: true
-        nodemailerdebug: true
-        body: CI workflow in ${{github.repository}} failed!
-          For details see "github.com/${{ github.repository }}/actions/runs/${{ github.run_id
-          }}"