fix(ci): adjust downgrade crates step (#7812)

.github/workflows/test-core.yml

@@ -85,7 +85,7 @@ jobs:
       - name: Downgrade crates with MSRV conflict
         # The --precise flag can only be used once per invocation.
         run: |
-          cargo update -p toml:0.7.6 --precise 0.7.3
+          cargo update -p toml:0.7.8 --precise 0.7.3
           cargo update -p toml_edit --precise 0.19.8
           cargo update -p toml_datetime --precise 0.6.1
           cargo update -p serde_spanned --precise 0.6.1
@@ -104,6 +104,8 @@ jobs:
           cargo update -p flate2 --precise 1.0.26
           cargo update -p h2 --precise 0.3.20
           cargo update -p reqwest --precise 0.11.18
+          cargo update -p cfg-expr:0.15.5 --precise 0.15.4
+          cargo update -p memchr --precise 2.6.2
 
       - name: test
         run: cargo test --target ${{ matrix.platform.target }} ${{ matrix.features.args }}