There is still no way to remove the file manually however as stated previously it will auto remove the file when you generate a new one. It will also auto delete if the disk space gets low, in fact I have seen (on 7.x) low disk space cause issues generating a new tech support file because it filled up the space before it was done and then deleted itself
If you are concerned about disk space you can clear some pcaps and old logs/reports from the CLI, there are several support docs and posts with more details like https://knowledgebase.paloaltonetworks.com/KCSArticleDetail?id=kA10g000000ClaJCAS
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