chore: gitignore the conformance run-go build artifact

The 6.4 MB compiled run-go binary was accidentally checked in along
with the relicense commit. Remove it from version control and add a
.gitignore entry so future builds don't drag it back in.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: jt55401

.gitignore

@@ -34,3 +34,4 @@ conformance/runners/run-rust/Cargo.lock
 .idea/
 .vscode/
 *.swp
+conformance/runners/run-go