Update dawidd6/action-send-mail action to v18

Signed-off-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

.github/workflows/issue_pr_lock.yml

@@ -74,7 +74,7 @@ jobs:
           log-output: true
       - if: failure()
         name: Send job failure notification e-mail
-        uses: dawidd6/action-send-mail@42942bc2f8fba4e611b459a018967a6a7c78c68c # v17
+        uses: dawidd6/action-send-mail@94de994a9f6fffee200243214e17002e2920bb59 # v18
         with:
           server_address: ${{secrets.ACTION_MAIL_SERVER}}
           server_port: 465

.github/workflows/release.yml

@@ -196,7 +196,7 @@ jobs:
         run: cat email_body.txt
       - name: Send release notification e-mail
         # Ref: https://github.com/dawidd6/action-send-mail
-        uses: dawidd6/action-send-mail@42942bc2f8fba4e611b459a018967a6a7c78c68c # v17
+        uses: dawidd6/action-send-mail@94de994a9f6fffee200243214e17002e2920bb59 # v18
         with:
           server_address: ${{secrets.ACTION_MAIL_SERVER}}
           server_port: 465