🥢 Fix typos in FixedPointMathLib.sol

[BhariGowda]

Fix two NatSpec comment typos in FixedPointMathLib.sol:

1. begins == end → begin == end in both lerp() overloads
   (parameter is named begin, not begins)

2. Fix broken comment line split in mulDiv inverse computation

[github-actions]

Gas Snapshot Comparison Report

Generated at commit : fd81365, Compared to commit : ab96a83

Contract Name	Test Name	Main Gas	PR Gas	Diff
LibRLPWithCLZTest	testComputeAddressForLargeNonces()	1750	-	-
	testComputeAddressForSmallNonces()	997	-	-
	testComputeAddressOriginalForLargeNonces()	3495	-	-
	testComputeAddressOriginalForSmallNonces()	2088	-	-
	testRLPEncodeBytes()	250090	-	-
	testRLPEncodeBytes2()	155904	-	-
	testRLPEncodeList()	735942	-	-
	testRLPEncodeList2()	810708	-	-
	testRLPEncodeListEdgeCases()	1807743	-	-
	testRLPEncodeStringEdgeCases()	20424	-	-
	testRLPEncodeUint()	1175570	-	-
	testRLPPUint256()	363834	-	-
	test__codesize()	18292	-	-