Lint: Fixing cargo-readme

There was an issue with cargo-readme when relying
specifically on the version of rust which we have
for the tooling itself. Changing this to nightly
seems to have fixed the issue.

Signed-off-by: Larry Dewey <larry.dewey@amd.com>

.github/workflows/lint.yml

@@ -56,7 +56,7 @@ jobs:
       - uses: actions/checkout@v2
       - uses: actions-rs/toolchain@v1
         with:
-          toolchain: 1.70.0
+          toolchain: nightly
           profile: minimal
           override: true
       - run: cargo install cargo-readme