AzureActiveDirectoryService: Use UrlDecoder for base64 decoding

Bug: https://github.com/davido/gerrit-oauth-provider/issues/161
Change-Id: I6a803d30d4272dfbd1a70402a1dff23302317adb

src/main/java/com/googlesource/gerrit/plugins/oauth/AzureActiveDirectoryService.java

diff --git a/src/main/java/com/googlesource/gerrit/plugins/oauth/AzureActiveDirectoryService.java b/src/main/java/com/googlesource/gerrit/plugins/oauth/AzureActiveDirectoryService.java
index 81dc53f..49077fb 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/oauth/AzureActiveDirectoryService.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/oauth/AzureActiveDirectoryService.java
@@ -236,7 +236,7 @@
     // Extract the payload part from the JWT token (header.payload.signature) by retrieving
     // tokenParts[1].
     return gson.fromJson(
-        new String(Base64.getDecoder().decode(tokenParts[1]), StandardCharsets.UTF_8),
+        new String(Base64.getUrlDecoder().decode(tokenParts[1]), StandardCharsets.UTF_8),
         JsonObject.class);
   }
 }