Drop @container to next line in v2 context.

Co-authored-by: Will Abramson <[email protected]>

Author: msporny

contexts/credentials/v2

@@ -78,7 +78,8 @@
         },
         "proof": {
           "@id": "https://w3id.org/security#proof",
-          "@type": "@id", "@container": "@graph"
+          "@type": "@id", 
+          "@container": "@graph"
         },
         "verifiableCredential": {
           "@id": "https://www.w3.org/2018/credentials#verifiableCredential",