🐞 Fix groupSum sorting

[atarpara]

Description

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Checklist

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• Ran forge fmt?
• Ran forge test?

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[github-actions]

Gas Snapshot Comparison Report

Generated at commit : e03a631, Compared to commit : 4225d5f

Contract Name	Test Name	Main Gas	PR Gas	Diff
LibSortTest	testHasDuplicateGas()	769174	769634	460
	testInsertionSortInts()	79950	79973	23
	testInsertionSortPsuedorandom()	63575	63553	-22
	testSearchSorted()	118046	118069	23
	testSearchSortedBasicCases()	2200	2178	-22
	testSearchSortedInts()	120090	120068	-22
	testSearchSortedWithEmptyArray()	677	721	44
	testSortAddressesReversed()	45497	45520	23
	testSortAddressesSorted()	41133	41176	43
	testSortInts()	887851	887873	22
	testSortMostlySame()	65989	65967	-22
	testSortOriginalMostlySame()	207254	207232	-22
	testSortOriginalSorted()	141663	141641	-22
	testSortPsuedorandom()	140092	140070	-22
	testSortSorted()	34541	34564	23
	testSortTestOverhead()	103279	103257	-22
	testSortedDifferenceDifferential()	182422	182399	-23
	testSortedIntersectionDifferential()	208346	208324	-22
	testUniquifySorted()	1703	1660	-43
	testUniquifySortedAddress()	4010	4032	22
	testUniquifySortedWithEmptyArray()	545	523	-22
	test__codesize()	25386	26730	1344
	testGroupSumSigned()	-	6156	-