scripts: Fix twisterlib for ruff - B009

This fixes ruff linting error B009,
where getattr() was used with a
constant field name.

Signed-off-by: Lukasz Mrugala <lukaszx.mrugala@intel.com>

.ruff-excludes.toml

@@ -800,7 +800,6 @@
     "UP031",    # https://docs.astral.sh/ruff/rules/printf-string-formatting
 ]
 "./scripts/pylib/twister/twisterlib/harness.py" = [
-    "B009",     # https://docs.astral.sh/ruff/rules/get-attr-with-constant
     "B904",     # https://docs.astral.sh/ruff/rules/raise-without-from-inside-except
     "E501",     # https://docs.astral.sh/ruff/rules/line-too-long
     "F541",     # https://docs.astral.sh/ruff/rules/f-string-missing-placeholders

scripts/pylib/twister/twisterlib/harness.py

@@ -924,7 +924,7 @@ class HarnessImporter:
             if harness_name:
                 harness_class = getattr(thismodule, harness_name)
             else:
-                harness_class = getattr(thismodule, 'Test')
+                harness_class = thismodule.Test
             return harness_class()
         except AttributeError as e:
             logger.debug(f"harness {harness_name} not implemented: {e}")