call: remove useless segment override

src/call.asm

@@ -19,15 +19,15 @@ _start:
     mov bx, 0x6
     xor cx, cx
 a1:
-    cmp cx, [es:si+4]
+    cmp cx, [si+4]
     jge a2
-    lea ax, [es:si+bx]
+    lea ax, [si+bx]
     push ax
     add bl, 2
     inc cl
     jmp a1
 a2:
-    call far [es:si]
+    call far [si]
     pop bp
     pop di
     pop si