fix: Fix name in Testplan constructor

I messed this up with a mangled rebase in f328cbc. Change it back to
the correct value.

Signed-off-by: Rupert Swarbrick <rswarbrick@lowrisc.org>

Author: rswarbrick

src/dvsim/testplan.py

@@ -368,7 +368,7 @@ def __init__(self, tagged_filename: str, repo_top: Path, name: str) -> None:
                            name set in the testplan Hjson.
 
         """
-        self.name = None
+        self.name = name
         self.testpoints: list[Testpoint] = []
         self.covergroups: list[Covergroup] = []
         self.test_results_mapped = False