Clarify usageWarning conformance language in ExecutableValueSet

Change the cqfm-usageWarning extension fixed value to remove the following sentences: The value set expansion specifies the timestamp when the expansion was produced, SHOULD contain the parameters used for the expansion, and SHALL contain the codes that are obtained by evaluating the value set definition. If this is ONLY an executable value set, a distributable definition of the value set must be obtained to compute the updated expansion. Move these sentences to the "Definition" element of the profile so it shows up in the introductory table.