Replace deprecated HTTP.UTF_8 with Charsets.UTF_8

Change-Id: I2da2c67462043c046edf6a8ba1f99f9b46401fd7

github-oauth/src/main/java/com/googlesource/gerrit/plugins/github/oauth/OAuthProtocol.java

diff --git a/github-oauth/src/main/java/com/googlesource/gerrit/plugins/github/oauth/OAuthProtocol.java b/github-oauth/src/main/java/com/googlesource/gerrit/plugins/github/oauth/OAuthProtocol.java
index b986373..37b3fef 100644
--- a/github-oauth/src/main/java/com/googlesource/gerrit/plugins/github/oauth/OAuthProtocol.java
+++ b/github-oauth/src/main/java/com/googlesource/gerrit/plugins/github/oauth/OAuthProtocol.java
@@ -19,10 +19,10 @@
 import org.apache.http.client.entity.UrlEncodedFormEntity;
 import org.apache.http.client.methods.HttpPost;
 import org.apache.http.message.BasicNameValuePair;
-import org.apache.http.protocol.HTTP;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import com.google.common.base.Charsets;
 import com.google.common.base.Strings;
 import com.google.gson.Gson;
 import com.google.inject.Inject;
@@ -186,11 +186,7 @@
     nvps.add(new BasicNameValuePair("client_id", config.gitHubClientId));
     nvps.add(new BasicNameValuePair("client_secret", config.gitHubClientSecret));
     nvps.add(new BasicNameValuePair("code", request.getParameter("code")));
-    try {
-      post.setEntity(new UrlEncodedFormEntity(nvps, HTTP.UTF_8));
-    } catch (UnsupportedEncodingException e) {
-      // Will never happen
-    }
+    post.setEntity(new UrlEncodedFormEntity(nvps, Charsets.UTF_8));
 
     try {
       HttpResponse postResponse = http.execute(post);