[url] Simplify "." and ".." (#86)

Since %2e and %2E are already decoded in the parser (#77 / bee5ad8041adfe6fc676c527bbc3f3cf4562ef67), the definitions of single-dot path segment and double-dot path segment can be simplified to "." and ".."

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Reply to this email directly or view it on GitHub:
https://github.com/whatwg/url/issues/86