breeze: Clean up SVG Tiny 1.2 errors in button

Incorrect (from Tiny's perspective) use of SVG elements and attributes
occasionally produced a bunch of mysterious warnings from QtSvg parser:

qt.svg: <input>:303:258: Could not add child element to parent element because the types are incorrect.
qt.svg: <input>:303:463: Could not add child element to parent element because the types are incorrect.
qt.svg: <input>:303:659: Could not add child element to parent element because the types are incorrect.
qt.svg: <input>:303:913: Could not add child element to parent element because the types are incorrect.
qt.svg: <input>:303:1049: Could not add child element to parent element because the types are incorrect.
qt.svg: <input>:303:1251: Could not add child element to parent element because the types are incorrect.
qt.svg: <input>:303:1453: Could not add child element to parent element because the types are incorrect.
qt.svg: <input>:303:1631: Could not add child element to parent element because the types are incorrect.
qt.svg: <input>:303:1739: Could not add child element to parent element because the types are incorrect.
qt.svg: <input>:303:1980: Could not add child element to parent element because the types are incorrect.
qt.svg: <input>:303:2223: Could not add child element to parent element because the types are incorrect.

Not only the filename is missing (which is mostly Plasma's fault --
QGraphicsSvgItem reports it correctly), but even the line of off!

Jing validator, when executed against the official RelaxNG scheme
reports much much more errors, but those seem to be mostly harmless
false-positives.

Anyways, these text spans are just comments for designers who work on
the theme itself, and were never intended to be seen by end users.
Ideally, such type of content should be omitted from production version
of SVG, but the only preprocessing we are doing so far is gzipping
into *.svgz archive.

See also: https://bugreports.qt.io/browse/QTBUG-100143