Remove references to html plugins from dev-plugins.txt
Remove references to html plugins from dev-plugins.txt

pg-plugin-styling.txt looks like it has references
to the old Polymer-plugin based styling system as well.

Change-Id: I29f0af7567dfc6c0864d6cb3ecb1e49f8659bf63

GerritCodeReview/gerrit,GerritCodeReview/gerrit,GerritCodeReview/gerrit,GerritCodeReview/gerrit,GerritCodeReview/gerrit,GerritCodeReview/gerrit,GerritCodeReview/gerrit,GerritCodeReview/gerrit