Fix flaky Windows tests: dispose file watchers before removing tmp dirs

The afterEach cleanup in three discovery test files called
tmpDirRemoveCallback() before discovery.dispose(). On Windows, the file
system watchers held open handles on the temp directory, causing
rimrafSync to fail with ENOTEMPTY. Swapping the order ensures watchers
are released before the directory is deleted.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: cklin

extensions/ql-vscode/test/vscode-tests/minimal-workspace/common/vscode/file-path-discovery.test.ts

@@ -118,8 +118,8 @@ describe("FilePathDiscovery", () => {
   });
 
   afterEach(() => {
-    tmpDirRemoveCallback?.();
     discovery.dispose();
+    tmpDirRemoveCallback?.();
   });
 
   describe("initialRefresh", () => {

extensions/ql-vscode/test/vscode-tests/minimal-workspace/queries-panel/query-discovery.test.ts

@@ -53,8 +53,8 @@ describe("Query pack discovery", () => {
   });
 
   afterEach(() => {
-    tmpDirRemoveCallback?.();
     discovery.dispose();
+    tmpDirRemoveCallback?.();
   });
 
   describe("buildQueryTree", () => {

extensions/ql-vscode/test/vscode-tests/minimal-workspace/queries-panel/query-pack-discovery.test.ts

@@ -34,8 +34,8 @@ describe("Query pack discovery", () => {
   });
 
   afterEach(() => {
-    tmpDirRemoveCallback?.();
     discovery.dispose();
+    tmpDirRemoveCallback?.();
   });
 
   describe("findQueryPack", () => {