♻️ Fix LibString StringStorage test

[Vectorized]

Description

♻️

Checklist

Ensure you completed all of the steps below before submitting your pull request:

• Ran forge fmt?
• Ran forge test?

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[github-actions]

Gas Snapshot Comparison Report

Generated at commit : f75f533, Compared to commit : 1119dd9

Contract Name	Test Name	Main Gas	PR Gas	Diff
LibStringTest	testSetAndGetStringStorage()	2346687	2349824	3137
	testSimpleStringSetAndGetGas()	598545	598833	288
	testStringEscapeJSONHexEncode()	687848	690983	3135
	testStringPackAndUnpackOne()	710695	714163	3468
	testStringPackAndUnpackTwo()	3267360	1068248	-2199112
	testToStringPositiveNumberBrutalized()	563006	566170	3164
	testToStringUint256MaxBrutalized()	574373	577477	3104
	testToStringZeroBrutalized()	562515	565619	3104
	test__codesize()	49822	49972	150