Unpin CI miri toolchain

Fixed in nightly-2026-02-13.

Author: dtolnay

.github/workflows/ci.yml

@@ -99,10 +99,7 @@ jobs:
     timeout-minutes: 45
     steps:
       - uses: actions/checkout@v6
-      - uses: dtolnay/rust-toolchain@master
-        with:
-          toolchain: nightly-2026-02-11 # https://github.com/rust-lang/miri/issues/4855
-          components: miri, rust-src
+      - uses: dtolnay/rust-toolchain@miri
       - run: cargo miri setup
       - run: cargo miri test
         env: