Remove git MCP server: package doesn't exist on npm, git CLI suffices

@modelcontextprotocol/server-git is not published to npm (it's a
Python package). Agents already have git installed and can use it
directly, so the MCP wrapper is unnecessary.

apps/harness/Dockerfile

@@ -45,7 +45,6 @@ COPY --from=gitea-mcp-builder /usr/local/bin/gitea-mcp /usr/local/bin/gitea-mcp
 RUN npm install -g \
     @modelcontextprotocol/server-postgres \
     @modelcontextprotocol/server-filesystem \
-    @modelcontextprotocol/server-git \
     kubernetes-mcp-server
 
 RUN addgroup --system --gid 1001 nodejs