Kernel: Remove sys$getdtablesize()

I'm not sure why this was a syscall. If we need this we can add it in
LibC as a wrapper around sysconf(_SC_OPEN_MAX).

Kernel/Process.cpp

@@ -2653,12 +2653,6 @@ int Process::sys$ioctl(int fd, unsigned request, unsigned arg)
     return description->file().ioctl(*description, request, arg);
 }
 
-int Process::sys$getdtablesize()
-{
-    REQUIRE_PROMISE(stdio);
-    return m_max_open_file_descriptors;
-}
-
 int Process::sys$dup(int old_fd)
 {
     REQUIRE_PROMISE(stdio);

Kernel/Process.h

@@ -229,7 +229,6 @@ public:
     int sys$ptsname_r(int fd, char*, ssize_t);
     pid_t sys$fork(RegisterState&);
     int sys$execve(const Syscall::SC_execve_params*);
-    int sys$getdtablesize();
     int sys$dup(int oldfd);
     int sys$dup2(int oldfd, int newfd);
     int sys$sigaction(int signum, const sigaction* act, sigaction* old_act);

Kernel/Syscall.h

@@ -80,7 +80,6 @@ namespace Kernel {
     __ENUMERATE_SYSCALL(execve)               \
     __ENUMERATE_SYSCALL(geteuid)              \
     __ENUMERATE_SYSCALL(getegid)              \
-    __ENUMERATE_SYSCALL(getdtablesize)        \
     __ENUMERATE_SYSCALL(dup)                  \
     __ENUMERATE_SYSCALL(dup2)                 \
     __ENUMERATE_SYSCALL(sigaction)            \

Libraries/LibC/unistd.cpp

@@ -417,12 +417,6 @@ int isatty(int fd)
     return tcgetattr(fd, &dummy) == 0;
 }
 
-int getdtablesize()
-{
-    int rc = syscall(SC_getdtablesize);
-    __RETURN_WITH_ERRNO(rc, rc, -1);
-}
-
 int dup(int old_fd)
 {
     int rc = syscall(SC_dup, old_fd);

Libraries/LibC/unistd.h

@@ -113,7 +113,6 @@ int link(const char* oldpath, const char* newpath);
 int unlink(const char* pathname);
 int symlink(const char* target, const char* linkpath);
 int rmdir(const char* pathname);
-int getdtablesize();
 int dup(int old_fd);
 int dup2(int old_fd, int new_fd);
 int pipe(int pipefd[2]);