Align structure of LICENSE.txt to LICENSE file of CrateDB.
Align structure of LICENSE.txt to LICENSE file of CrateDB.

Before the change, `licensee` did not properly detect the project as
Apache2-licensed. Now, it does.

$ licensee
License:        Apache-2.0
Matched files:  LICENSE.txt
LICENSE.txt:
  Content hash:  bec905d850e7f5dc2e2db78a950d4a9db560a0b8
  Confidence:    100.00%
  Matcher:       Licensee::Matchers::Exact
  License:       Apache-2.0
crate/docker-crate,crate/docker-crate