[ci] fix link to LightGBM public e-mail (#4603)

.github/workflows/r_solaris.yml

@@ -48,7 +48,7 @@ jobs:
               url=${line#*@}
               body="${body}**${platform}**: ${url}\r\n"
           done < "$GITHUB_WORKSPACE/rhub_logs.txt" || true
-          body="${body}Reports also have been sent to LightGBM public e-mail: http://www.yopmail.com/lightgbm_rhub_checks\r\n"
+          body="${body}Reports also have been sent to LightGBM public e-mail: https://yopmail.com?lightgbm_rhub_checks\r\n"
           body="${body}Status: ${{ job.status }}."
           $GITHUB_WORKSPACE/.ci/append_comment.sh \
             "${{ github.event.client_payload.comment_number }}" \