I believe this experience was quite frustrating for you, for me it was for sure. The main problem is, both the files, flume-sources-1.0-SNAPSHOT.jar and twitter4j-stream-3.0.3.jar contains the same FilterQuery.class. That is why the conflict message is generated in the log file.
I am not a Java or Big Data expert, but I can give you an alternate to this problem. Download the Twitter4j-stream-2.6.6.jar or lower version from here and replacethe twitter4j-stream-3.0.3.jar. All the 3.X.X uses this class. After replacing, everything should work fine. But you may get some heap error after downloading huge amount of tweets. Please google the solution as it was resolved in 3.X.X files.
-Edit Also, please don't forget to download and replace all the twitter4j files in /usr/lib/flume-ng folder. Namely, twitter4j-media-support-2.2.6.jar, twitter4j-stream-2.2.6.jar and twitter4j-core-2.2.6.jar. Any mismatch related to version among these files will also create problem.