test(core): use backslash Windows path style in pwsh detection test

Match the file's existing convention for Windows path literals
(see line 521: 'C:\Program Files\PowerShell\7\pwsh.exe' and
line 613: path.resolve('C:\Windows\System32')).

Author: kaluchi

packages/core/src/utils/shell-utils.test.ts

@@ -486,7 +486,7 @@ describe('getShellConfiguration', () => {
     });
 
     it('should prefer pwsh.exe over powershell.exe when pwsh is available in PATH', () => {
-      const pwshDir = path.resolve('/Program Files/PowerShell/7');
+      const pwshDir = path.resolve('C:\\Program Files\\PowerShell\\7');
       const pwshPath = path.join(pwshDir, 'pwsh.exe');
       vi.stubEnv('PATH', pwshDir);
       mockAccessSync.mockImplementation((p: string) => {