Removed stable from github actions

Temporarily removed stable as a rust option for github actions. This should be reverted when 1.74 is made the rustc stable version and is only due to the ICE error being presently resolved in nightly. This leads to some clear instability with nightly features, but it's currently the only option

.github/workflows/rust.yml

@@ -10,7 +10,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        rust: [stable, nightly]
+        rust: [nightly]  # This should be reverted back to [stable, nightly] when 1.74 is made the rustc stable version
     env:
       CRATE_NAME: gluon
       CARGO_INCREMENTAL: 0 # Incremental compilation is slower and bloats the cache