Remove workaround for BS4/5 compatibility

[PhilippImhof]

fixes #179

[coveralls]

Pull Request Test Coverage Report for Build 14420692267

Details

• 0 of 1 (0.0%) changed or added relevant line in 1 file are covered.
• 14 unchanged lines in 2 files lost coverage.
• Overall coverage remained the same at 95.807%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
renderer.php	0	1	0.0%

Files with Coverage Reduction	New Missed Lines	%
renderer.php	1	92.53%
backup/moodle2/restore_qtype_formulas_plugin.class.php	13	56.96%

Totals
Change from base Build 14313833033:	0.0%
Covered Lines:	3770
Relevant Lines:	3935

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💛 - Coveralls