Fix StackOverflowError during hash code computation

I7659ae66b provided wrong implementation of hashCode(). Objects.hash()
calls Arrays.hashCode(values) on provided values, which in turn calls
hashCode() on its parameters, which in turn leads to endless recursion,
and in the end to StackOverflowError error.

Change-Id: I709239cbd27592765319b15c13044ab9aad738c0

gerrit-gwtui/src/main/java/com/google/gerrit/client/diff/LineMapper.java

@@ -195,7 +195,7 @@ class LineMapper {
 
     @Override
     public int hashCode() {
-      return Objects.hash(this);
+      return Objects.hash(line, aligned);
     }
 
     @Override