add bcmath to dockers

[stephenwaite]

Fixes #

Short description of what this resolves:

https://floating-point-gui.de/

Changes proposed in this pull request:

[bradymiller]

hi @stephenwaite ,

Don't need flex 3.19 since really not used anymore.

Note that no way to get this fix into a 7.0.3 patch since folks don't update the docker when they bring a patch into it. ok to bring it in to the 7.0.3 docker, but need to assume 7.0.3 users will not have it. Also note that can only build 7.0.3 docker during patch releases and before do it need to increment the 2 patch tags at https://github.com/openemr/openemr-devops/blob/master/.github/workflows/build-703.yml#L28
(note there is a way to rebuild docker on a current patch if needed, but would need to grab the tag rather than the branch at: https://github.com/openemr/openemr-devops/blob/master/docker/openemr/7.0.3/Dockerfile#L24)

After bring this in regarding building:
Note flex-edge and 7.0.4 autobuild every night, so those will be covered.
Then just need to manual build from actions for flex-3.18, flex-3.20, flex-3.21

After that will also need to add the package to all the demo farm dockers (not tough and I am happy to build/push them to dockerhub since haven't created github actions for those).