Fix `IntMaskOfTest::testToString()` #292

Job	Run time
Coding Standards / Coding Standards (8.0)	36s
Code Coverage / Code Coverage	31s
Static analysis / Static Code Analysis (8.0)	37s
Lint root / Lint yaml & Composer (8.0)	15s
Dependency analysis / Dependency Analysis (8.0)	32s
Unit test / Supported Versions Matrix	4s
Unit test / Tests (7.4, locked)	45s
Unit test / Tests (8.0, lowest)	51s
Unit test / Tests (7.4, highest)	40s
Unit test / Tests (8.0, highest)	45s
Unit test / Tests (8.0, locked)	47s
Unit test / Tests (7.4, lowest)	59s
Unit test / Tests (8.1, lowest)	35s
Unit test / Tests (8.1, locked)	42s
Unit test / Tests (8.2, locked)	29s
Unit test / Tests (8.4, locked)	47s
Unit test / Tests (8.2, lowest)	50s
Unit test / Tests (8.1, highest)	33s
Unit test / Tests (8.3, highest)	49s
Unit test / Tests (8.4, highest)	57s
Unit test / Tests (8.2, highest)	59s
Unit test / Tests (8.4, lowest)	34s
Unit test / Tests (8.3, lowest)	1m 3s
Unit test / Tests (8.5, lowest)	46s
Unit test / Tests (8.3, locked)	47s
Unit test / Tests (8.5, locked)	59s
Unit test / Tests (8.5, highest)	1m 1s
	19m 13s

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