Fix astsee tests

Author: wsnyder

t/t_dump_json_astsee.py

@@ -13,7 +13,7 @@
 test.top_filename = os.environ["VERILATOR_ROOT"] + "/test_regress/t/t_dump.v"
 
 out = test.run_capture("astsee_verilator -h 2>&1", check=False)
-if 'not found' in out:
+if 'usage:' not in out:
     test.skip("No astsee installed\n")
 
 test.lint(v_flags=["--lint-only --dump-tree-json"])

t/t_gdb_jtree.py

@@ -13,7 +13,7 @@
 test.top_filename = "t/t_dump.v"
 
 out = test.run_capture("astsee_verilator -h 2>&1", check=False)
-if 'not found' in out:
+if 'usage:' not in out:
     test.skip("No astsee installed\n")
 
 test.setenv(