fix: remove non-existent test/rust directory from CI

The test/rust directory doesn't exist, causing CI to fail with
'no targets found beneath test/rust'.

Existing test directories are:
- test/go (Go component tests - validates our hermetic toolchain)
- test/cpp (C++ component tests)
- test/unit, test/integration (general tests)

This allows CI to proceed and validate our working hermetic Go
toolchain implementation.

Author: avrabe

.github/workflows/ci.yml

@@ -116,7 +116,6 @@ jobs:
             //wit/... \
             //tools/... \
             //providers/... \
-            //test/rust/... \
             //test/go/... \
             //test/cpp/... \
             //test/unit/... \