Shrink SVG icons even a bit more

In looking at the code produced by GeneratePress, it appears there is some unnecessary markup used for SVG icons which can be removed to shrink the size and speed the loading of icons even further...

In particular, these two declarations are not needed in the code produced:

xmlns:xlink="http://www.w3.org/1999/xlink"

version="1.1"

It's not a massive gain, but it's free and every little bit helps! Add up 57 bytes saved here and there, and pretty soon we're talking about real money... :)

References:

https://medium.com/@peternowell/stuff-at-the-top-of-an-svg-f3ad198eb54e

https://developer.mozilla.org/en-US/docs/Web/SVG/Namespaces_Crash_Course#Declaring_namespace_prefixes