Simplify contentToString function

Authored by Daimona on Thu, May 10, 8:34 AM.

Description

Simplify contentToString function

Use TextContent::normalizeLineEndings instead of manually replacing
carriage returns, plus avoid the if with a simple string cast. This also
fixes some cases where a null edit isn't counted as such due to a "\n"
in new_wikitext which isn't trimmed.

Bug: T168736
Change-Id: Idfafab3fcf7912bf0aec22700d2c0137bdd6c3c8

Details