Update Migration Documentation about Library/$evaluate

[AndyStevens98]

In v0.4.0, CQF Ruler's Library/$evaluate operation provided results as a Bundle of Parameters and in version v0.5.0, the Library/$evaluate operation provides results as a single Parameters resource (as defined in the CPG FHIR IG). Applications may make use of this operation and noting the difference in output structure would be great to include in the migration documentation.