[polymer] Remove special logic for importing the gzip importer
[polymer] Remove special logic for importing the gzip importer

It wasn't necessary because the gzip importer is already included
recursively through chrome_config.html.

NOPRESUBMIT=true
NOTRY=true
BUG=catapult:#2285

Review-Url: https://codereview.chromium.org/2136153002

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