Pin CI miri to nightly-2026-02-11

Author: dtolnay

.github/workflows/ci.yml

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