Remove obsolete comments.

src/rt/arch/i386/morestack.S

@@ -201,9 +201,6 @@ MORESTACK:
 	// Save the return value of the function we allocated space for
 	movl %eax, (%esp)
 
-	// Now that we're on the return path we want to avoid
-	// stomping on %eax. FIXME: Need to save and restore %eax to
-	// actually preserve it across the call to delete the stack
 	call UPCALL_DEL_STACK
 
 	// And restore it

src/rt/arch/x86_64/morestack.S

@@ -103,7 +103,6 @@ MORESTACK:
 	// Save the return value
 	pushq %rax
 
-	// FIXME: Should preserve %rax here
 #ifdef __APPLE__
 	call UPCALL_DEL_STACK
 #endif