Update CI for rand_core

Author: dhardy

.github/workflows/test.yml

@@ -117,9 +117,8 @@ jobs:
           cargo test --target ${{ matrix.target }} --features=serde,log,small_rng
       - name: Test rand_core
         run: |
-          cargo test --target ${{ matrix.target }} --manifest-path rand_core/Cargo.toml
           cargo test --target ${{ matrix.target }} --manifest-path rand_core/Cargo.toml --no-default-features
-          cargo test --target ${{ matrix.target }} --manifest-path rand_core/Cargo.toml --no-default-features --features=os_rng
+          cargo test --target ${{ matrix.target }} --manifest-path rand_core/Cargo.toml --features serde
       - name: Test rand_pcg
         run: cargo test --target ${{ matrix.target }} --manifest-path rand_pcg/Cargo.toml --features=serde
       - name: Test rand_chacha