asdf_library is redundant to history.extensions

[braingram]

asdf-standard/resources/stable/schemas/stsci.edu/asdf/core/asdf-1.0.0.yaml

Lines 13 to 16 in 748b94a

	asdf_library:
	description: |
	Describes the ASDF library that produced the file.
	$ref: "software-1.0.0"

contains a single software entry for the library that produced the file.

This information is also present in history.extensions:

asdf-standard/resources/stable/schemas/stsci.edu/asdf/core/asdf-1.1.0.yaml

Lines 39 to 50 in 748b94a

	definitions:
	history-1.1.0:
	type: object
	properties:
	extensions:
	type: array
	items:
	- $ref: "extension_metadata-1.0.0"
	entries:
	type: array
	items:
	- $ref: "history_entry-1.0.0"

To use a small example file:

>> print(asdf.dumps({"foo": "bar"}).decode("ascii"))
#ASDF 1.0.0
#ASDF_STANDARD 1.6.0
%YAML 1.1
%TAG ! tag:stsci.edu:asdf/
--- !core/asdf-1.1.0
asdf_library: !core/software-1.0.0 {author: The ASDF Developers, homepage: 'http://github.com/asdf-format/asdf',
  name: asdf, version: 5.0.1.dev0+g10f536301.d20250919}
history:
  extensions:
  - !core/extension_metadata-1.0.0
    extension_class: asdf.extension._manifest.ManifestExtension
    extension_uri: asdf://asdf-format.org/core/extensions/core-1.6.0
    manifest_software: !core/software-1.0.0 {name: asdf_standard, version: 1.1.1}
    software: !core/software-1.0.0 {name: asdf, version: 5.0.1.dev0+g10f536301.d20250919}
foo: bar
...

Note the same version in history.extensions[0].software and asdf_library. (Note that only name and version are required the author in asdf_library could also occur in history.extensions).

I propose that we remove asdf_library.