Fix return type of tkinter.Text.search_all()

[Akuli]

It returns a tuple of _tkinter.Tcl_Obj:

akuli@Akuli-Desktop ~/sourcestuff/Python-3.15.0b1 $ ./python 
Python 3.15.0b1 (main, May 11 2026, 17:35:51) [GCC 14.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import tkinter
>>> t = tkinter.Text()
>>> t.pack()
>>> t.insert('end', 'hello world test thingy hello test')
>>> t.search_all('t', '1.0')
(<textindex object: '1.12'>, <textindex object: '1.15'>, <textindex object: '1.17'>, <textindex object: '1.30'>, <textindex object: '1.33'>)
>>> list(map(type,_))
[<class '_tkinter.Tcl_Obj'>, <class '_tkinter.Tcl_Obj'>, <class '_tkinter.Tcl_Obj'>, <class '_tkinter.Tcl_Obj'>, <class '_tkinter.Tcl_Obj'>]

[github-actions]

Diff from mypy_primer, showing the effect of this PR on open source code:

pandas (https://github.com/pandas-dev/pandas)
+ pandas/core/computation/ops.py:328: error: Need type annotation for "_binary_ops_dict" (hint: "_binary_ops_dict: dict[<type>, <type>] = ...")  [var-annotated]