Tests failing due to issues building wheels for `so3` and `pyssht`

[matt-graham]

Several jobs in the last scheduled run of the tests workflow failed. It looks like this is due to errors when attempting to build wheels for the so3 and pyssht packages required for running the tests, with for some of the jobs pre-built or cached wheels for these packages being picked up which is allowing the tests to run successfully. For both pyssht and so3 the error seems to be caused by a CMake error when attempting to build fftw

       fftw/3.3.10: Aggregating env generators
      fftw/3.3.10: Calling build()
      fftw/3.3.10: apply_conandata_patches(): No patches defined in conandata
      fftw/3.3.10: CMake command: cmake -G "Unix Makefiles" -DCMAKE_TOOLCHAIN_FILE="/home/runner/.conan/data/fftw/3.3.10/_/_/build/76fb618e9f590ad1830f3b3f412b2dc9af0b6433/build/Release/generators/conan_toolchain.cmake" -DCMAKE_INSTALL_PREFIX="/home/runner/.conan/data/fftw/3.3.10/_/_/package/76fb618e9f590ad1830f3b3f412b2dc9af0b6433" -DCMAKE_POLICY_DEFAULT_CMP0091="NEW" -DCMAKE_BUILD_TYPE="Release" -DENABLE_FLOAT="ON" -DENABLE_LONG_DOUBLE="OFF" -DENABLE_QUAD_PRECISION="OFF" "/home/runner/.conan/data/fftw/3.3.10/_/_/build/76fb618e9f590ad1830f3b3f412b2dc9af0b6433/src"
      CMake Error at CMakeLists.txt:1 (cmake_minimum_required):
        Compatibility with CMake < 3.5 has been removed from CMake.
      
        Update the VERSION argument <min> value.  Or, use the <min>...<max> syntax
        to tell CMake that the project requires at least <min> but has been updated
        to work with policies introduced by <max> or earlier.
      
        Or, add -DCMAKE_POLICY_VERSION_MINIMUM=3.5 to try configuring anyway.

which appears to be related to FFTW/fftw3#381