Fix authorization token Bearer prefix spelling in examples;

the prefix should be spelled exactly as "Bearer", see
RFC 6750, section 2.1. Authorization Request Header Field
https://datatracker.ietf.org/doc/html/rfc6750#section-2.1

openid-4-verifiable-credential-issuance-1_0.md

@@ -760,7 +760,7 @@ Below is a non-normative example of a Credential Request for a Credential in [@I
 POST /credential HTTP/1.1
 Host: server.example.com
 Content-Type: application/json
-Authorization: BEARER czZCaGRSa3F0MzpnWDFmQmF0M2JW
+Authorization: Bearer czZCaGRSa3F0MzpnWDFmQmF0M2JW
 
 {
   "format":"mso_mdoc",
@@ -780,7 +780,7 @@ Below is a non-normative example of a Credential Request for two Credential inst
 POST /credential HTTP/1.1
 Host: server.example.com
 Content-Type: application/json
-Authorization: BEARER czZCaGRSa3F0MzpnWDFmQmF0M2JW
+Authorization: Bearer czZCaGRSa3F0MzpnWDFmQmF0M2JW
 
 {
   "credential_identifier": "CivilEngineeringDegree-2023",
@@ -1086,7 +1086,7 @@ The following is a non-normative example of a Deferred Credential Request:
 POST /deferred_credential HTTP/1.1 
 Host: server.example.com
 Content-Type: application/json
-Authorization: BEARER czZCaGRSa3F0MzpnWDFmQmF0M2JW
+Authorization: Bearer czZCaGRSa3F0MzpnWDFmQmF0M2JW
 
 {
   "transaction_id": "8xLOxBtZp8"