Write out LICENSE.enterprise

https://github.com/coder/coder/blob/5362f4636ef9b588c71d99d2bee5bd942207ddce/LICENSE.enterprise#L1-L9

is inadequate.

	LICENSE (GNU Affero General Public License) applies to
	all files in this repository, except for those in or under
	any directory named "enterprise", which are Copyright Coder
	Technologies, Inc., All Rights Reserved.

	We plan to release an enterprise license covering these files
	as soon as possible. Watch this space.

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