Remove TODO from kernel.Stracer

The dependency strace=>kernel grew over time. strace also depends on
task's FD table and FSContext. It could be fixed with some interfaces
the other way, but then we're trading an interface for another, and
kernel.Stracer is likely cleaner.

Closes #155

PiperOrigin-RevId: 305909678

pkg/sentry/kernel/syscalls.go

@@ -209,9 +209,6 @@ type Stracer interface {
 	// SyscallEnter is called on syscall entry.
 	//
 	// The returned private data is passed to SyscallExit.
-	//
-	// TODO(gvisor.dev/issue/155): remove kernel imports from the strace
-	// package so that the type can be used directly.
 	SyscallEnter(t *Task, sysno uintptr, args arch.SyscallArguments, flags uint32) interface{}
 
 	// SyscallExit is called on syscall exit.

pkg/sentry/strace/strace.go

@@ -778,9 +778,6 @@ func (s SyscallMap) Name(sysno uintptr) string {
 //
 // N.B. This is not in an init function because we can't be sure all syscall
 // tables are registered with the kernel when init runs.
-//
-// TODO(gvisor.dev/issue/155): remove kernel package dependencies from this
-// package and have the kernel package self-initialize all syscall tables.
 func Initialize() {
 	for _, table := range kernel.SyscallTables() {
 		// Is this known?