update CE display name to reflect branch and codegen path

Author: g-ampo

contrib/godbolt/rust-cuda.defaults.properties

@@ -18,7 +18,7 @@ compiler=/opt/compiler-explorer/rust-cuda/bin/rust-cuda-wrapper.sh
 lang=rust
 
 # Human-readable name in the compiler selector.
-name=rust-cuda (nightly-2026-04-02)
+name=rust-cuda main (llvm7)
 
 # Semantic version used for sorting in the compiler list.
 semver=0.3.0