Add no-extra-rounding-error flag to Miri CI config

Author: okaneco

.github/workflows/ci.yml

@@ -244,5 +244,10 @@ jobs:
       PROPTEST_CASES: 16
     steps:
       - uses: actions/checkout@v4
+      - name: Download and install nightly
+        run: |
+          rustup toolchain install nightly --component miri,rust-src
+          rustup override set nightly
+          cargo miri setup
       - name: Test (Miri)
-        run: cargo miri test
+        run: MIRIFLAGS="-Zmiri-no-extra-rounding-error" cargo miri test