Revert "ci: add miri"

Miri is currently generating "reached the type-length limit while
instantiating" error in sqlx. Removing until we figure out how to fix
it.

This reverts commit b85831c.

.github/workflows/rust.yml

@@ -135,29 +135,3 @@ jobs:
 
       - name: Run fmt
         run: cargo fmt --all -- --check
-
-  miri:
-    if: github.event_name == 'push' || github.event_name == 'schedule' ||
-      github.event.pull_request.head.repo.full_name != github.repository
-
-    name: Undefined behaviour checks
-    runs-on: ubuntu-latest
-    needs: ["build"]
-    steps:
-      - name: Checkout source
-        uses: actions/checkout@v4
-
-      - name: Install Rust toolchain
-        uses: dtolnay/rust-toolchain@master
-        with:
-          toolchain: nightly
-          components: miri
-
-      - name: Cache Cargo registry
-        uses: Swatinem/rust-cache@v2
-
-      - name: Setup Miri
-        run: cargo miri setup
-
-      - name: Run Miri
-        run: cargo miri test