Fix typo - 'MUST but' -> 'MUST be'

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

@@ -1109,7 +1109,7 @@ Authorization: Bearer czZCaGRSa3F0MzpnWDFmQmF0M2JW
 }
 ```
 
-The Credential Issuer indicates support for encrypted responses by including the `credential_response_encryption` parameter in the Credential Issuer Metadata. The Client MAY request encrypted responses by providing its encryption parameters in the Deferred Credential Request when `encryption_required` is `false` and MUST do so when `encryption_required` is `true`. Note that this object will be used for encrypting the response, regardless of what was sent in the initial Credential Request. If it is not included encryption will not be performed. Deferred Credential Request encryption MUST but used if the `credential_response_encryption` parameter is included, to prevent it being substituted by an attacker.
+The Credential Issuer indicates support for encrypted responses by including the `credential_response_encryption` parameter in the Credential Issuer Metadata. The Client MAY request encrypted responses by providing its encryption parameters in the Deferred Credential Request when `encryption_required` is `false` and MUST do so when `encryption_required` is `true`. Note that this object will be used for encrypting the response, regardless of what was sent in the initial Credential Request. If it is not included encryption will not be performed. Deferred Credential Request encryption MUST be used if the `credential_response_encryption` parameter is included, to prevent it being substituted by an attacker.
 
 ## Deferred Credential Response {#deferred-credential-response}
 

1.1/openid-4-verifiable-credential-issuance-1_1.md

@@ -1516,7 +1516,7 @@ Authorization: Bearer czZCaGRSa3F0MzpnWDFmQmF0M2JW
 }
 ```
 
-The Credential Issuer indicates support for encrypted responses by including the `credential_response_encryption` parameter in the Credential Issuer Metadata. The Client MAY request encrypted responses by providing its encryption parameters in the Deferred Credential Request when `encryption_required` is `false` and MUST do so when `encryption_required` is `true`. Note that this object will be used for encrypting the response, regardless of what was sent in the initial Credential Request. If it is not included encryption will not be performed. Deferred Credential Request encryption MUST but used if the `credential_response_encryption` parameter is included, to prevent it being substituted by an attacker.
+The Credential Issuer indicates support for encrypted responses by including the `credential_response_encryption` parameter in the Credential Issuer Metadata. The Client MAY request encrypted responses by providing its encryption parameters in the Deferred Credential Request when `encryption_required` is `false` and MUST do so when `encryption_required` is `true`. Note that this object will be used for encrypting the response, regardless of what was sent in the initial Credential Request. If it is not included encryption will not be performed. Deferred Credential Request encryption MUST be used if the `credential_response_encryption` parameter is included, to prevent it being substituted by an attacker.
 
 ## Deferred Credential Response {#deferred-credential-response}