typing: Replace objects from typing with literals

We also replace the use of typing.Union and add missing parameters and
returns types for Callable types.

Change-Id: I75ed4d1cc4d84515910a5bd315f8626135258148
Signed-off-by: Stephen Finucane <stephenfin@redhat.com>

doc/ext/extra_specs.py

@@ -18,7 +18,6 @@ Provides a single directive that can be used to list all extra specs validators
 and, thus, document all extra specs that nova recognizes and supports.
 """
 
-import typing as ty
 
 from docutils import nodes
 from docutils.parsers import rst
@@ -90,7 +89,7 @@ def _indent(text, count=1):
 
 
 def _format_validator_group_help(
-    validators: ty.Dict[str, base.ExtraSpecValidator],
+    validators: dict[str, base.ExtraSpecValidator],
     summary: bool,
 ):
     """Generate reStructuredText snippets for a group of validators."""