build: remove artifacts to please emqx forked rebar3

[qzhuyan]

No description provided.

[coveralls]

Pull Request Test Coverage Report for Build 7008404800

Warning: This coverage report may be inaccurate.

We've detected an issue with your CI configuration that might affect the accuracy of this pull request's coverage report.
To ensure accuracy in future PRs, please see these guidelines.
A quick fix for this PR: rebase it; your next report should be accurate.

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 6 unchanged lines in 3 files lost coverage.
• Overall coverage decreased (-0.07%) to 82.874%

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Files with Coverage Reduction	New Missed Lines	%
src/quicer.erl	1	88.89%
c_src/quicer_stream.c	2	84.99%
c_src/quicer_nif.c	3	76.88%

Totals
Change from base Build 7006314934:	-0.07%
Covered Lines:	3431
Relevant Lines:	4140

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💛 - Coveralls