Update OAuth2 token info API docs to be clearer

The token info endpoint was added to the GitLab repo after upgrading to
Doorkeeper 5.0.2 to ensure we could maintain backwards compatibility
with this endpoint after the upgrade.

Update the docs that were added as part of this change to be clearer and
more consistent.

doc/api/oauth2.md

@@ -215,21 +215,24 @@ curl --header "Authorization: Bearer OAUTH-TOKEN" https://gitlab.example.com/api
 
 ## Retrieving the Token Info
 
-To verify the details of a token you can call the `token/info` endpoint. This is provided from the doorkeeper gem (see [`/oauth/token/info`](https://github.com/doorkeeper-gem/doorkeeper/wiki/API-endpoint-descriptions-and-examples#get----oauthtokeninfo)).
+To verify the details of a token, use the `token/info` endpoint provided by the Doorkeeper gem.
+For more information, see [`/oauth/token/info`](https://github.com/doorkeeper-gem/doorkeeper/wiki/API-endpoint-descriptions-and-examples#get----oauthtokeninfo).
 
-You will need to supply the access token, either as a parameter
+You must supply the access token, either:
 
-```
-GET https://gitlab.example.com/oauth/token/info?access_token=OAUTH-TOKEN
-```
+- As a parameter:
 
-Or in the Authorization header:
+   ```
+   GET https://gitlab.example.com/oauth/token/info?access_token=<OAUTH-TOKEN>
+   ```
 
-```
-curl --header "Authorization: Bearer OAUTH-TOKEN" https://gitlab.example.com/oauth/token/info
-```
+- In the Authorization header:
 
-You will receive the following in response:
+   ```shell
+   curl --header "Authorization: Bearer <OAUTH-TOKEN>" https://gitlab.example.com/oauth/token/info
+   ```
+
+The following is an example response:
 
 ```json
 {
@@ -241,5 +244,11 @@ You will receive the following in response:
 }
 ```
 
-CAUTION: **Deprecated fields:**
-The fields `scopes` and `expires_in_seconds` are also included in the response. They are aliases for `scope` and `expires_in` respectively and have been included to prevent breaking changes introduced in [doorkeeper 5.0.2](https://github.com/doorkeeper-gem/doorkeeper/wiki/Migration-from-old-versions#from-4x-to-5x). Please don't rely on these fields as they will be removed in a later release.
+### Deprecated fields
+
+The fields `scopes` and `expires_in_seconds` are included in the response.
+
+These are aliases for `scope` and `expires_in` respectively, and have been included to
+prevent breaking changes introduced in [doorkeeper 5.0.2](https://github.com/doorkeeper-gem/doorkeeper/wiki/Migration-from-old-versions#from-4x-to-5x).
+
+Don't rely on these fields as they will be removed in a later release.