Kernel: Mark sys$mremap as not needing the big lock

All accesses to shared mutable data are already serialized behind the
process address space spinlock.

Kernel/API/Syscall.h

@@ -128,7 +128,7 @@ enum class NeedsBigProcessLock {
     S(mmap, NeedsBigProcessLock::No)                       \
     S(mount, NeedsBigProcessLock::Yes)                     \
     S(mprotect, NeedsBigProcessLock::No)                   \
-    S(mremap, NeedsBigProcessLock::Yes)                    \
+    S(mremap, NeedsBigProcessLock::No)                     \
     S(msync, NeedsBigProcessLock::Yes)                     \
     S(munmap, NeedsBigProcessLock::No)                     \
     S(open, NeedsBigProcessLock::No)                       \

Kernel/Syscalls/mmap.cpp

@@ -480,7 +480,7 @@ ErrorOr<FlatPtr> Process::sys$munmap(Userspace<void*> addr, size_t size)
 
 ErrorOr<FlatPtr> Process::sys$mremap(Userspace<Syscall::SC_mremap_params const*> user_params)
 {
-    VERIFY_PROCESS_BIG_LOCK_ACQUIRED(this);
+    VERIFY_NO_PROCESS_BIG_LOCK(this);
     TRY(require_promise(Pledge::stdio));
     auto params = TRY(copy_typed_from_user(user_params));