Use jgit @NonNull annotation

Use the same null analysis annotations which are used in gerrit and
jgit.

Change-Id: I2c8adb065793f27d9d3c144889e19ff8178e438a
diff --git a/src/main/java/com/googlesource/gerrit/plugins/aicodereview/config/Configuration.java b/src/main/java/com/googlesource/gerrit/plugins/aicodereview/config/Configuration.java
index 74a687c..40a9a79 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/aicodereview/config/Configuration.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/aicodereview/config/Configuration.java
@@ -31,7 +31,7 @@
 import lombok.extern.slf4j.Slf4j;
 import org.apache.http.NameValuePair;
 import org.apache.http.message.BasicNameValuePair;
-import org.jetbrains.annotations.NotNull;
+import org.eclipse.jgit.annotations.NonNull;
 
 @Slf4j
 public class Configuration {
@@ -407,7 +407,7 @@
     return Double.parseDouble(getString(key, String.valueOf(defaultValue)));
   }
 
-  @NotNull
+  @NonNull
   private static <T extends Enum<T>> T getValueAsEnum(Class<T> enumClass, String value) {
     try {
       return Enum.valueOf(enumClass, value);