BUG: apexpy not routinely tested

[jklenzing]

Description

The main.yml workflow currently never attempts to install apexpy. Current configs are set toif: ${{ matrix.numpy_ver != 'latest' && matrix.os == 'macos-latest' }} and if: ${{ matrix.numpy_ver != 'latest' && matrix.os != 'macos-latest' }}, which are never True because only ubuntu is tested for older numpy versions.

With the fixes in apexpy 2.1.0, we can reconfigure based on the external_rc workflow so that it always tries to install. The continue_on_error setting can still be True since these are optional installs.

To Reproduce this bug:

Inspect the main.yml workflow results.

Test configuration

GitHub Actions main.yml

Additional context

aacgmv2 is now working regularly with the latest release. We should update apexpy tests as well.