bpo-37734: Remove unnecessary brace escapes in PC/layout script (GH-15165)

(cherry picked from commit 0378d98)

Co-authored-by: Steve Dower <[email protected]>

Author: miss-islington

PC/layout/support/appxmanifest.py

@@ -156,7 +156,7 @@
             "SysVersion": VER_DOT,
             "Version": "{}.{}.{}".format(VER_MAJOR, VER_MINOR, VER_MICRO),
             "InstallPath": {
-                "": "[{{AppVPackageRoot}}]",
+                "": "[{AppVPackageRoot}]",
                 "ExecutablePath": "[{{AppVPackageRoot}}]\\python{}.exe".format(VER_DOT),
                 "WindowedExecutablePath": "[{{AppVPackageRoot}}]\\pythonw{}.exe".format(VER_DOT),
             },