SquishTests: Update repository of Creator's sources to v6.0.1

6.0.1 was released on Qt 6.2 and was the last
version which could be built on Qt 5.14.

How I got to this:
0. Verify on Linux that the test passes with qbs 2.0.2
   from Creator 10 to have a combination which is known
   to work correctly.
1. Upgrade sources to v6.0.1 and write the tree which
   qbs 2.0.2 and Creator 11 generated from those.
2. Run the test with qbs 2.1.0 and Creator 11 and update
   the expected tree. This only meant removing a couple
   of lines.
3. Verify on Windows that the test passes with qbs 2.0.2
   from Creator 10 to have a combination which is known
   to work correctly.
4. Upgrade sources to v6.0.1 and write the tree which
   qbs 2.0.2 and Creator 11 generated from those. Remove
   all lines from the expected tree which were not found.
   Most of those contained forward slashes instead of
   backslashes.
5. Verify that the result passes with qbs 2.1.0 and
   Creator 11

Change-Id: I41579feb719324cf1fc605c73fe1d7566cf82202
Reviewed-by: Christian Stenger <christian.stenger@qt.io>
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>

tests/system/README

@@ -36,8 +36,8 @@ Qt 6.2.4 (MSVC2019, 64bit)
 Third - you'll have to provide some additional repositories.
 These additional repositories are located inside ~/squish-data or C:\Users\<user>\squish-data (depending on the OS you're on).
 You can also just provide them inside a different folder and specify the folder with the environment variable SYSTEST_SRCPATH.
-This folder must contain a QtCreator repository (or source copy) of tag v4.7.0 named 'creator'
-including the submodule src/shared/qbs
+This folder must contain a QtCreator repository (or source copy) of tag v6.0.1 named 'creator'
+without any submodules initialized.
 
 Fourth - you'll have to make sure that some needed tools are available (no matter on which OS you're on).
  * cmake 3.14 or newer