Bump minimal version in ci to 1.76

Author: DRiKE

.github/workflows/ci.yml

@@ -7,7 +7,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest, windows-latest, macOS-latest]
-        rust: [1.71, stable, beta]
+        rust: [1.76, stable, beta]
     steps:
       - name: Checkout repository
         uses: actions/checkout@v1