Fix weight decay in line search #82

Job	Run time
Check (ubuntu-latest, stable)	27s
Test Suite (ubuntu-latest, stable)	1m 53s
Check (ubuntu-latest, beta)	31s
Test Suite (ubuntu-latest, beta)	2m 7s
Check (ubuntu-latest, nightly)	30s
Test Suite (ubuntu-latest, nightly)	1m 47s
Check (windows-latest, stable)	1m 10s
Test Suite (windows-latest, stable)	3m 17s
Check (windows-latest, beta)	1m 4s
Test Suite (windows-latest, beta)	3m 51s
Check (windows-latest, nightly)	1m 7s
Test Suite (windows-latest, nightly)	3m 34s
Check (macOS-latest, stable)	1m 1s
Test Suite (macOS-latest, stable)	3m 43s
Check (macOS-latest, beta)	54s
Test Suite (macOS-latest, beta)	4m 28s
Check (macOS-latest, nightly)	55s
Test Suite (macOS-latest, nightly)	2m 23s
	34m 42s

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