Remove `callback` arg to webkit print preview

mypy 1.11 has new and improved support for checking partial functions,
and it works great! It says:

    qutebrowser/components/misccommands.py: note: In function "_print_preview":
    qutebrowser/components/misccommands.py:74: error: Unexpected keyword argument "callback" for "to_printer" of
    "AbstractPrinting"  [call-arg]
            diag.paintRequested.connect(functools.partial(
                                        ^
    qutebrowser/browser/browsertab.py:269: note: "to_printer" of "AbstractPrinting" defined here

We indeed removed the callback arg in 377749c76f

And running `:print --preview` on webkit crashes with:

    TypeError: WebKitPrinting.to_printer() got an unexpected keyword argument 'callback'

With this change print preview works again (on webkit), which I'm a
little surprised by!

qutebrowser/components/misccommands.py

@@ -9,7 +9,6 @@
 
 import os
 import signal
-import functools
 import logging
 import pathlib
 from typing import Optional, Sequence, Callable
@@ -60,10 +59,6 @@ def stop(tab: Optional[apitypes.Tab]) -> None:
 
 def _print_preview(tab: apitypes.Tab) -> None:
     """Show a print preview."""
-    def print_callback(ok: bool) -> None:
-        if not ok:
-            message.error("Printing failed!")
-
     tab.printing.check_preview_support()
     diag = QPrintPreviewDialog(tab)
     diag.setAttribute(Qt.WidgetAttribute.WA_DeleteOnClose)
@@ -71,8 +66,7 @@ def _print_preview(tab: apitypes.Tab) -> None:
         diag.windowFlags() |
         Qt.WindowType.WindowMaximizeButtonHint |
         Qt.WindowType.WindowMinimizeButtonHint)
-    diag.paintRequested.connect(functools.partial(
-        tab.printing.to_printer, callback=print_callback))
+    diag.paintRequested.connect(tab.printing.to_printer)
     diag.exec()