chore: Bump MSRV to 1.65

Allows to use let-else statements.

.github/workflows/ci.yml

@@ -65,7 +65,7 @@ jobs:
         run: target/debug/xtask ci lint
 
   msrv:
-    name: Rust 1.64 / ${{ matrix.name }}
+    name: Rust 1.65 / ${{ matrix.name }}
     needs: xtask
     runs-on: ubuntu-latest
     strategy:
@@ -90,17 +90,17 @@ jobs:
       - name: Checkout repo
         uses: actions/checkout@v3
 
-      - name: Install rust 1.64 toolchain
+      - name: Install rust 1.65 toolchain
         uses: dtolnay/rust-toolchain@master
         with:
-          toolchain: 1.64
+          toolchain: 1.65
 
       - uses: Swatinem/rust-cache@v2
         with:
           # A stable compiler update should automatically not reuse old caches.
           # Add the MSRV as a stable cache key too so bumping it also gets us a
           # fresh cache.
-          sharedKey: msrv1.64
+          sharedKey: msrv1.65
 
       - name: Get xtask
         uses: actions/cache@v3