libsigrok: migrate to python@3.14

[branchvincent]

libsigrok: migrate to python@3.14

[Copilot]

Pull Request Overview

This PR migrates the libsigrok formula from Python 3.13 to Python 3.14 by updating the dependency specification and the python3 helper method.

• Updated dependency from python@3.13 to python@3.14
• Updated the python3 method to return "python3.14" instead of "python3.13"

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[branchvincent]

  ../../../bindings/python/sigrok/core/../../../swig/classes.i:51: Warning 330: Template forward class 'enable_shared_from_this< Context >' cannot be used to instantiate a full template class with name 'ContextShared'.
  sigrok/core/classes_wrap.cpp: In function ‘int SWIG_mod_exec(PyObject*)’:
  sigrok/core/classes_wrap.cpp:62265:12: error: cannot convert ‘std::nullptr_t’ to ‘int’ in return
  62265 |     return nullptr;
        |            ^~~~~~~
  error: command '/home/linuxbrew/.linuxbrew/Homebrew/Library/Homebrew/shims/linux/super/g++-12' failed with exit code 1
  make[1]: *** [Makefile:5290: bindings/python/timestamp] Error 1
  make: *** [Makefile:1992: all] Error 2