Adjust test_errors_in_xfail_skip_expressions for PyPy

It appears that newer PyPy versions have a different syntax error marker
offset. This patch stripps 7 whitespaces off of the marker line.

Author: x612skm

testing/test_skipping.py

@@ -1140,8 +1140,8 @@ def test_func():
     result = pytester.runpytest()
     markline = "            ^"
     pypy_version_info = getattr(sys, "pypy_version_info", None)
-    if pypy_version_info is not None and pypy_version_info < (6,):
-        markline = markline[1:]
+    if pypy_version_info is not None:
+        markline = markline[7:]
 
     if sys.version_info >= (3, 10):
         expected = [