Revert "Temporarily disable miri on doctests"

This reverts commit 6259d49.

Author: dtolnay

.github/workflows/ci.yml

@@ -88,7 +88,7 @@ jobs:
       - uses: actions/checkout@v4
       - uses: dtolnay/rust-toolchain@miri
       - run: cargo miri setup
-      - run: cargo miri test --all-targets  # exclude doctests https://github.com/rust-lang/miri/issues/3404
+      - run: cargo miri test
         env:
           MIRIFLAGS: -Zmiri-strict-provenance