fix: remove unused grep override tool from E2E test

The ErgonomicToolDefinitionIT snapshot only exercises set_current_phase
and search_items. The grep tool (with overridesBuiltInTool=true) was
never invoked, making it dead code that contradicted the PR description.

Addresses review comment r3469523851.

Author: edburns

java/src/test/java/com/github/copilot/e2e/ErgonomicTestTools$$CopilotToolMeta.java

@@ -44,15 +44,6 @@ public List<ToolDefinition> definitions(ErgonomicTestTools instance, ObjectMappe
                             Map<String, Object> args = invocation.getArguments();
                             String keyword = (String) args.get("keyword");
                             return CompletableFuture.completedFuture(instance.searchItems(keyword));
-                        }, null, null, null),
-                new ToolDefinition("grep", "Custom grep override",
-                        Map.of("type", "object", "properties", Map.ofEntries(Map.entry("query",
-                                (Map<String, Object>) (Map) withMeta(Map.of("type", "string"), "Search query", null))),
-                                "required", List.of("query")),
-                        invocation -> {
-                            Map<String, Object> args = invocation.getArguments();
-                            String query = (String) args.get("query");
-                            return CompletableFuture.completedFuture(instance.grepOverride(query));
-                        }, Boolean.TRUE, null, null));
+                        }, null, null, null));
     }
 }

java/src/test/java/com/github/copilot/e2e/ErgonomicTestTools.java

@@ -29,9 +29,4 @@ public String setCurrentPhase(@Param("The phase to transition to") String phase)
     public String searchItems(@Param("Search keyword") String keyword) {
         return "Found: item_alpha, item_beta";
     }
-
-    @CopilotTool(value = "Custom grep override", name = "grep", overridesBuiltInTool = true)
-    public String grepOverride(@Param("Search query") String query) {
-        return "CUSTOM_GREP: " + query;
-    }
 }