Fix inaccurate `read_string_from_stdin` migration info.

tutorials/migrating/upgrading_to_godot_4.4.rst

@@ -45,7 +45,7 @@ Method ``store_string`` changes return type from ``void`` to ``bool``
 Method ``store_var`` changes return type from ``void`` to ``bool``                                                        |✔️|                 |❌|                  |✔️|                  `GH-78289`_
 **OS**
 Method ``execute_with_pipe`` adds a new ``blocking`` optional parameter                                                   |✔️|                 |✔️ with compat|      |✔️ with compat|      `GH-94434`_
-Method ``read_string_from_stdin`` adds a new ``buffer_size`` optional parameter                                           |✔️|                 |✔️ with compat|      |✔️ with compat|      `GH-91201`_
+Method ``read_string_from_stdin`` adds a new ``buffer_size`` parameter [#f1]_                                             |❌|                 |✔️ with compat|      |✔️ with compat|      `GH-91201`_
 **RegEx**
 Method ``compile`` adds a new ``show_error`` optional parameter                                                           |✔️|                 |✔️ with compat|      |✔️ with compat|      `GH-95212`_
 Method ``create_from_string`` adds a new ``show_error`` optional parameter                                                |✔️|                 |✔️ with compat|      |✔️ with compat|      `GH-95212`_
@@ -55,6 +55,8 @@ Method ``post`` adds a new ``count`` optional parameter
 Method ``standardize_locale`` adds a new ``add_defaults`` optional parameter                                              |✔️|                 |✔️ with compat|      |✔️ with compat|      `GH-98972`_
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+.. [#f1] Default buffer size in 4.3 is ``1024``.
+
 GUI nodes
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