Tests: Remove CPython test submodules, they only do harm

* We need to organize their relationship externally, in
  CI runs, but as it is now, they only do harm when e.g.
  using Git URLs in pyproject.toml with tools.

.gitmodules

@@ -1,48 +0,0 @@
-[submodule "tests/CPython26"]
-    path = tests/CPython26
-    url = https://github.com/Nuitka/Nuitka-CPython-tests.git
-    branch = CPython26
-[submodule "tests/CPython27"]
-    path = tests/CPython27
-    url = https://github.com/Nuitka/Nuitka-CPython-tests.git
-    branch = CPython27
-[submodule "tests/CPython32"]
-    path = tests/CPython32
-    url = https://github.com/Nuitka/Nuitka-CPython-tests.git
-    branch = CPython32
-[submodule "tests/CPython33"]
-    path = tests/CPython33
-    url = https://github.com/Nuitka/Nuitka-CPython-tests.git
-    branch = CPython33
-[submodule "tests/CPython34"]
-    path = tests/CPython34
-    url = https://github.com/Nuitka/Nuitka-CPython-tests.git
-    branch = CPython34
-[submodule "tests/CPython35"]
-    path = tests/CPython35
-    url = https://github.com/Nuitka/Nuitka-CPython-tests.git
-    branch = CPython35
-[submodule "tests/CPython36"]
-    path = tests/CPython36
-    url = https://github.com/Nuitka/Nuitka-CPython-tests.git
-    branch = CPython36
-[submodule "tests/CPython37"]
-    path = tests/CPython37
-    url = https://github.com/Nuitka/Nuitka-CPython-tests.git
-    branch = CPython37
-[submodule "tests/CPython38"]
-    path = tests/CPython38
-    url = https://github.com/Nuitka/Nuitka-CPython-tests.git
-    branch = CPython38
-[submodule "tests/CPython39"]
-    path = tests/CPython39
-    url = https://github.com/Nuitka/Nuitka-CPython-tests.git
-    branch = CPython39
-[submodule "tests/CPython310"]
-    path = tests/CPython310
-    url = https://github.com/Nuitka/Nuitka-CPython-tests.git
-    branch = CPython310
-[submodule "tests/CPython311"]
-    path = tests/CPython311
-    url = https://github.com/Nuitka/Nuitka-CPython-tests.git
-    branch = CPython311