Exclude rust_optimizer_error_test.cpp from Bazel build

This test requires the Rust FFI header which is only available
when building with spirv_tools_enable_rust=true.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: LegNeato

BUILD.bazel

@@ -522,6 +522,7 @@ cc_library(
         "test/rust_validator_override_test.cpp",
         "test/rust_disassembler_diagnostics_test.cpp",
         "test/disassemble_rust_fallback_test.cpp",
+        "test/rust_optimizer_error_test.cpp",
     ],
 )]