Remove sanitizeUrl function

What does this MR do and why?

Relates to Improvements in app/assets/javascripts/lib/util... (#467984)

Remove sanitizeUrl function

The sanitation that sanitizeUrl offers is minimal. It returns about:blank for invalid URLs. sanitizeUrl is used only once.

Internally, sanitizeUrl uses isValidURL (and new URL(...)) to decide if a URL is valid. In the only place that sanitizeUrl is used, I haven't found a way to make the URL /${this.projectPath}/-/error_tracking/${errorId}.json invalid. Even if we found a way, the user will be puzzled to navigate to a about:blank page.

I suggest we remove the sanitizeUrl function.

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