Dependencies: remove temporary upper limit for sqlalchemy

[sphuber]

This reverts 383ab247c40ada60c22ce3673cbbc3efccd21f98. The upper limit
is no longer necessary as the incompatibility of sqlalchemy-utils with
sqlalchemy==1.4 has been solved downstream.

[sphuber]

This is still failing because the limit in aiida-core has not been released yet. We have two options here:

1. Once aiida-core==1.6.2 is released with the upped requirement of sqlalchemy-utils, we depend on that version of aiida-core and we remove the dependency limit on sqlalchemy here or
2. We simply remove the sqlalchemy limit here now and add a minimum requirement on sqlalchemy-utils.

Writing it out like this, it seems clear that 2) is the much favored option as we can keep supporting more versions of aiida-core.

EDIT: never mind, aiida-core adds the dependency sqlalchemy-utils~=0.34.2 which is incompatible with what we would like to have sqlalchemy-utils

[sphuber]

Just released aiida-core==1.5.3 which fixes the compatibility issues with sqlalchemy and psycopg2-binary, so this can now be merged.