Remove go:nosplit from IncrementUnimplementedSyscallCounter

This enables the runsc binary to be build with `-c dbg`.

PiperOrigin-RevId: 657283482

pkg/sentry/kernel/syscalls.go

@@ -500,8 +500,6 @@ type SyscallInfo struct {
 // FIXME(gvisor.dev/issue/10556): checkescape can't distinguish between this
 // file and files named syscalls.go in other directories, resulting in false
 // positives, so this function cannot be +checkescape:all.
-//
-//go:nosplit
 func IncrementUnimplementedSyscallCounter(sysno uintptr) {
 	s, found := unimplementedSyscallNumbers[sysno]
 	if !found {