Update EHR access requirement (fixes #315) (#405)

Author: brettmarquard

docs/specification/1.0.md

@@ -207,8 +207,9 @@ An EHR MAY choose to honor some or all of the desired prefetch templates, and is
 
 - The EHR may have some of the desired prefetched data already in memory, thereby removing the need for any network call
 - The EHR may compute an efficient set of prefetch templates from multiple CDS Services, thereby reducing the number of network calls to a minimum
-- The EHR may satisfy some of the desired prefetched templates via some internal service or even its own FHIR server
-- The EHR may deny access because the requested resource is outside the user's authorized context.
+- The EHR may satisfy some of the desired prefetched templates via some internal service or even its own FHIR server.
+
+The EHR SHALL deny access if the requested resource is outside the user's authorized context.
 
 Regardless of how the EHR satisfies the prefetch templates (if at all), the prefetched data given to the CDS Service MUST be equivalent to the data the CDS Service would receive if it were making its own call to the EHR FHIR server using the parameterized prefetch template.