-k should not match session name

Fixes https://github.com/pytest-dev/pytest/issues/7040.

changelog/7040.improvement.rst

@@ -0,0 +1 @@
+``-k`` no longer matches against the directory containing the test suite.

src/_pytest/mark/__init__.py

@@ -136,7 +136,7 @@ class KeywordMatcher:
         import pytest
 
         for item in item.listchain():
-            if not isinstance(item, pytest.Instance):
+            if not isinstance(item, (pytest.Instance, pytest.Session)):
                 mapped_names.add(item.name)
 
         # Add the names added as extra keywords to current or parent items