CI: upgrade to Rust 1.70.0

Signed-off-by: Miguel Ojeda <[email protected]>

Author: ojeda

.github/workflows/ci.yaml

@@ -7,7 +7,7 @@ on:
 jobs:
   ci:
     runs-on: ubuntu-20.04
-    container: ghcr.io/rust-for-linux/ci:Rust-1.66.0
+    container: ghcr.io/rust-for-linux/ci:Rust-1.70.0
     timeout-minutes: 25
 
     strategy: