Match spec error code "invalid context entry".

Tests were also using "invalid context member" and have been updated to
match the spec.

Author: davidlehn

CHANGELOG.md

@@ -12,6 +12,7 @@
   whitespace.
 - Terms of the form of an IRI must map to the same IRI.
 - Terms of the form of a relative IRI may not be used as prefixes.
+- Match spec error code "invalid context entry" vs "invalid context member".
 
 ### Changed
 - Keep term definitions mapping to null so they may be protected.

lib/context.js

@@ -255,7 +255,7 @@ api.process = async ({
           'Invalid JSON-LD syntax; @propagate not compatible with ' +
           activeCtx.processingMode,
           'jsonld.SyntaxError',
-          {code: 'invalid context member', context: ctx});
+          {code: 'invalid context entry', context: ctx});
       }
       if(typeof value !== 'boolean') {
         throw new JsonLdError(