ci: Change GH-Actions comment to DFU download link (#1163)

Change the GitHub Actions bot comment to directly point to the full
firmware DFU download link.
Include a pointer to the qFlipper documentation to guide folks towards
installing the DFU file.
The WebUSB flashing link can be restored in the future if it returns.
See https://forum.flipperzero.one/t/no-database-found-after-firmware-update/1761/6

Co-authored-by: あく <alleteam@gmail.com>

.github/workflows/build.yml

@@ -161,7 +161,7 @@ jobs:
           comment-id: ${{ steps.fc.outputs.comment-id }}
           issue-number: ${{ github.event.pull_request.number }}
           body: |
-            [Click here](https://update.flipperzero.one/?url=https://update.flipperzero.one/builds/firmware/${{steps.names.outputs.artifacts-path}}/flipper-z-${{steps.names.outputs.default-target}}-full-${{steps.names.outputs.suffix}}.dfu&channel=${{steps.names.outputs.artifacts-path}}&version=${{steps.names.outputs.short-hash}}&target=${{steps.names.outputs.default-target}}) to flash the `${{steps.names.outputs.short-hash}}` version of this branch via WebUSB.
+            [Click here](https://update.flipperzero.one/builds/firmware/${{steps.names.outputs.artifacts-path}}/flipper-z-${{steps.names.outputs.default-target}}-full-${{steps.names.outputs.suffix}}.dfu) for the DFU file to flash the `${{steps.names.outputs.short-hash}}` version of this branch with the [`Install from file` option in qFlipper](https://docs.flipperzero.one/basics/firmware-update).
           edit-mode: replace
 
   compact: