Account for how canvas handles icon size

[ajbozarth]

Canvas wraps svgs in a second svg tag that sets the icon width and height.
This doesn't work if the svg already sets those values, so I removed the width and height from the icons on the backend to compensate.
The new values are in line with the icons provided by JupyterLab.

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[akchinSTC]

unfortunately still seeing the issue, it only affects the python icon, everything else is fine

[akchinSTC]

ensure browser cache is cleared for localhost or where-ever elyra is being hosted

[ptitzler]

icons lgtm now