test: Add missing MCP tests to ai-g1 group in groups.json

Added 7 MCP tests that were missing from the ai-g1 group:
- mcp_mixed_mysql_pgsql_concurrency_stress-t
- mcp_mixed_stats_cap_churn-t
- mcp_mixed_stats_profile_matrix-t
- mcp_mysql_concurrency_stress-t
- mcp_pgsql_concurrency_stress-t
- mcp_show_queries_topk-t
- mcp_stats_refresh-t

test/tap/groups/groups.json

@@ -273,9 +273,16 @@
   "genai_async-t": [ "ai-g1" ],
   "genai_embedding_rerank-t": [ "ai-g1" ],
   "genai_module-t": [ "ai-g1" ],
+  "mcp_mixed_mysql_pgsql_concurrency_stress-t": [ "ai-g1" ],
+  "mcp_mixed_stats_cap_churn-t": [ "ai-g1" ],
+  "mcp_mixed_stats_profile_matrix-t": [ "ai-g1" ],
   "mcp_module-t": [ "ai-g1" ],
-  "mcp_show_connections_commands_inmemory-t": [ "ai-g1" ],
+  "mcp_mysql_concurrency_stress-t": [ "ai-g1" ],
+  "mcp_pgsql_concurrency_stress-t": [ "ai-g1" ],
   "mcp_query_run_sql_readonly-t": [ "ai-g1" ],
+  "mcp_show_connections_commands_inmemory-t": [ "ai-g1" ],
+  "mcp_show_queries_topk-t": [ "ai-g1" ],
+  "mcp_stats_refresh-t": [ "ai-g1" ],
   "nl2sql_integration-t": [ "ai-g1" ],
   "nl2sql_internal-t": [ "ai-g1" ],
   "nl2sql_model_selection-t": [ "ai-g1" ],