Fix test_gmt_compat_6_is_applied

Author: seisman

pygmt/tests/test_session_management.py

@@ -36,10 +36,8 @@ def test_gmt_compat_6_is_applied(capsys):
     """
     end()  # Kill the global session
     try:
-        # Generate a gmt.conf file in the current directory
-        # with GMT_COMPATIBILITY = 5
-        with Session() as lib:
-            lib.call_module("gmtset", ["GMT_COMPATIBILITY=5"])
+        # Generate a gmt.conf file in the current directory with GMT_COMPATIBILITY = 5
+        Path("gmt.conf").write_text("GMT_COMPATIBILITY = 5", encoding="utf-8")
         begin()
         with Session() as lib:
             lib.call_module("basemap", ["-R10/70/-3/8", "-JX4i/3i", "-Ba"])