multimedia/onevpl: respect PYTHON_DEFAULT

$ pkg install python311
$ make -V PYTHON_DEFAULT
3.8
$ make clean all
[...]

• Found Python3: /usr/local/bin/python3.11 (found version "3.11.0") found components: Interpreter Development Development.Module Development.Embed

[...]
CMake Warning:

Manually-specified variables were not used by the project:

[...]

Python_ADDITIONAL_VERSIONS

[...]
$ make check-plist

> Checking for pkg-plist issues (check-plist)

> Parsing plist

> Checking for items in STAGEDIR missing from pkg-plist

Error: Orphaned: %%PYTHON_LIBDIR%%/pyvpl.cpython-311.so

> Checking for items in pkg-plist which are not in STAGEDIR

Error: Missing: %%PYTHON_LIBDIR%%/pyvpl%%PYTHON_EXT_SUFFIX%%.so

> Error: Plist issues found.

• Error code 1

PR: 261415
(cherry picked from commit 0378719b21c61d5a5d3dc8f31be7781fd7ff11ef)