findDependencies.cmake: use FindPython instead of deprecated FindPythonInterp

[firewave]

This fixes the following warning with CMake 3.27:

CMake Warning (dev) at cmake/findDependencies.cmake:42 (find_package):
  Policy CMP0148 is not set: The FindPythonInterp and FindPythonLibs modules
  are removed.  Run "cmake --help-policy CMP0148" for policy details.  Use
  the cmake_policy command to set the policy and suppress this warning.

Call Stack (most recent call first):
  CMakeLists.txt:15 (include)
This warning is for project developers.  Use -Wno-dev to suppress it.