docs: fix description of `py.install_sources` arguments

There is actually very little overlap between `install_sources` and
`install_data` in arguments they accept: only 2/7 keywords for `install_data`
apply to `install_sources`.

Closes gh-12601

docs/markdown/Python-module.md

@@ -158,11 +158,8 @@ void py_installation.install_sources(list_of_files, ...)
 
 Install actual python sources (`.py`).
 
-All positional and keyword arguments are the same as for
-[[install_data]], with the addition of the following:
-
-*Since 0.60.0* `python.platlibdir` and `python.purelibdir` options can be used
-to control the default installation path. See [Python module options](Builtin-options.md#python-module).
+Source files to install are given as positional argument, in the same way as for
+[[install_data]]. Supported keyword arguments are:
 
 - `pure`: On some platforms, architecture independent files are
   expected to be placed in a separate directory. However, if the
@@ -177,6 +174,12 @@ to control the default installation path. See [Python module options](Builtin-op
 - `install_tag` *(since 0.60.0)*: A string used by `meson install --tags` command
   to install only a subset of the files. By default it has the tag `python-runtime`.
 
+- `preserve_path`: if `true`, disable stripping child-directories from data
+  files when installing. Default is `false`. *(since 0.64.0)*
+
+*Since 0.60.0* `python.platlibdir` and `python.purelibdir` options can be used
+to control the default installation path. See [Python module options](Builtin-options.md#python-module).
+
 #### `get_install_dir()`
 
 ``` meson