asdf-format / asdf

AsdfSpec (based off of SimpleSpec from semantic_version) is effectively unused.

It is referenced once in format_tag:

Lines 20 to 21 in aedf156

    
           if isinstance(version, AsdfSpec): 
        
               version = str(version.spec)

format_tag has only a single use in asdf:

Line 841 in aedf156

    
           tag = asdf.testing.helpers.format_tag("stsci.edu", "asdf", "1.0.0", "fits/fits")

where a spec is not provided.

The format_tag use can be replaced by an f-string.

One motivation for deprecating AsdfSpec is that it provides unexpected version comparisons: see #1772

	if isinstance(version, AsdfSpec):
	version = str(version.spec)

deprecate `AsdfSpec` and `format_tag`