chore(deps): bump the actions group with 2 updates

Bumps the actions group with 2 updates: [actions/cache](https://github.com/actions/cache) and [dawidd6/action-send-mail](https://github.com/dawidd6/action-send-mail).


Updates `actions/cache` from 5.0.5 to 6.1.0
- [Release notes](https://github.com/actions/cache/releases)
- [Changelog](https://github.com/actions/cache/blob/main/RELEASES.md)
- [Commits](actions/cache@27d5ce7...55cc834)

Updates `dawidd6/action-send-mail` from 6e502825a508b867ab2954ad6343b68787624c01 to 994f270325d4f7257aff241a35488ef54ba364a4
- [Release notes](https://github.com/dawidd6/action-send-mail/releases)
- [Commits](dawidd6/action-send-mail@6e50282...994f270)

---
updated-dependencies:
- dependency-name: actions/cache
  dependency-version: 6.1.0
  dependency-type: direct:production
  update-type: version-update:semver-major
  dependency-group: actions
- dependency-name: dawidd6/action-send-mail
  dependency-version: 994f270325d4f7257aff241a35488ef54ba364a4
  dependency-type: direct:production
  dependency-group: actions
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

.github/workflows/agda.yml

@@ -119,7 +119,7 @@ jobs:
       # source change or absolute-zero bump; restore-keys give a warm
       # partial cache even when it does.
       - name: Cache Agda interface files
-        uses: actions/cache@27d5ce7f107fe9357f9df03efb73ab90386fccae # v5.0.5
+        uses: actions/cache@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6.1.0
         with:
           path: |
             ~/agda-stdlib/**/*.agdai

.github/workflows/push-email-notify.yml

@@ -15,7 +15,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Send push notification email
-        uses: dawidd6/action-send-mail@6e502825a508b867ab2954ad6343b68787624c01 # pinned
+        uses: dawidd6/action-send-mail@994f270325d4f7257aff241a35488ef54ba364a4 # pinned
         with:
           server_address: ${{ secrets.SMTP_HOST }}
           server_port: ${{ secrets.SMTP_PORT }}