Reduce target-version to py312

Co-authored-by: Adam Turner <9087854+AA-Turner@users.noreply.github.com>

Author: mhsmith

Lib/test/.ruff.toml

@@ -1,6 +1,6 @@
 extend = "../../.ruff.toml"  # Inherit the project-wide settings
 
-target-version = "py313"
+target-version = "py312"
 
 extend-exclude = [
     # Excluded (run with the other AC files in its own separate ruff job in pre-commit)
@@ -16,7 +16,10 @@ extend-exclude = [
 ]
 
 [per-file-target-version]
-# t-strings
+# Type parameter defaults
+"test_type_params.py" = "py313"
+
+# Template string literals
 "test_annotationlib.py" = "py314"
 "test_string/test_templatelib.py" = "py314"
 "test_tstring.py" = "py314"