Release Notes: Standardize on asciidoc attributes

Replace some hugo frontmatter variables with inline asciidoc attributes
We were using a mix of the two, and commonizing made sense

The syntax for showing an asciidoc attribute {var} is cleaner than
the hugo {{% param var %}} syntax as well

Also, asciidoc attributes are literal, and must not be quoted or the
quotes will show up in the content

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