Remove secp256k1 benchmark #263

Job	Run time
linux-x86-ci-generated	13s
linux-x86-deny	55s
linux-x86-ci (ubuntu-latest)	38s
linux-x86-ci (ubuntu-24.04-arm)	1m 7s
linux-native-ci-asm (ubuntu-latest)	42s
linux-native-test-suite (ubuntu-latest)	1m 59s
linux-native-ci-asm (ubuntu-24.04-arm)	1m 12s
windows-x86-ci-asm	2m 55s
linux-native-test-suite (ubuntu-24.04-arm)	5m 0s
linux-native-ci-asm-chaos (ubuntu-24.04-arm)	1m 20s
linux-native-ci-asm-chaos (ubuntu-latest)	49s
linux-arm-ci-asm	6m 26s
linux-native-test-spawn (ubuntu-latest)	39s
linux-fuzz	4m 42s
linux-native-test-spawn (ubuntu-24.04-arm)	1m 33s
linux-arm-test-suite	5m 15s
macos-x86-ci-asm	1m 46s
	37m 11s

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