mongodb 3.4.10 has unpatched CVEs and mongodb 3.4.24 has some files in the
release tarball under the SSPL, therefore we cannot provide mongodb while
upholding to good security standards.

It turns out feff80ce was right since while
the main license file wasnt altered to SSPL, some files in the tree contain
SSPL headers.

* gnu/packages/databases.scm (go-gopkg.in-mgo.v2): Remove.
* gnu/packages/databases.scm (mongo-tools): Remove.
* doc/guix.texi (mongodb-service-type): Remove.
* gnu/tests/databases.scm (%test-mongodb, %mongodb-os, run-mongodb-test):
Remove.
* gnu/services/databases.scm (mongodb-configuration, mongodb-configuration?,
mongodb-configuration-mongodb, mongodb-configuration-config-file,
mongodb-configuration-data-directory, mongodb-service-type,
%default-mongodb-configuration-file, %mongodb-accounts, mongodb-activation,
mongodb-shepherd-service): Remove.
* gnu/packages/databases.scm (mongodb): Remove.