fix: correct MIME type of .txt files (ref: #6762) (#7111)

Co-authored-by: Lucas Nogueira <lucas@tauri.app>

.github/workflows/test-core.yml

@@ -93,6 +93,7 @@ jobs:
           cargo update -p time --precise 0.3.15
           cargo update -p ignore --precise 0.4.18
           cargo update -p raw-window-handle --precise 0.5.0
+          cargo update -p cargo_toml:0.15.3 --precise 0.15.2
 
       - name: test
         run: cargo test --target ${{ matrix.platform.target }} ${{ matrix.features.args }}