Tests: pin plone.schema to 1.4.0 in Plone 4.3.

[mauritsvanrees]

@tisto I wanted to create a release of 7.x.x for the upcoming Plone 5.2 release, but saw the build was broken. This should fix it.

This plone.schema is the latest version compatible with Python 2. On Plone 5.0 and higher this package is already pinned. A Python 3 only version was released on April 6th, and broke the build: https://github.com/plone/plone.restapi/actions/runs/4635281794/jobs/8202199547

Traceback (most recent call last):
  File "/home/runner/work/plone.restapi/plone.restapi/src/plone/restapi/tests/test_behaviors.py", line 7, in <module>
    from plone.restapi.behaviors import IBlocks
  File "/home/runner/work/plone.restapi/plone.restapi/src/plone/restapi/behaviors.py", line 4, in <module>
    from plone.schema import JSONField
  File "/home/runner/work/plone.restapi/plone.restapi/eggs/plone.schema-2.0.0-py2.7.egg/plone/schema/__init__.py", line 3, in <module>
    from .jsonfield import IJSONField
  File "/home/runner/work/plone.restapi/plone.restapi/eggs/plone.schema-2.0.0-py2.7.egg/plone/schema/jsonfield.py", line 1, in <module>
    from json import JSONDecodeError
ImportError: cannot import name JSONDecodeError

[mister-roboto]

@mauritsvanrees thanks for creating this Pull Request and helping to improve Plone!

TL;DR: Finish pushing changes, pass all other checks, then paste a comment:

@jenkins-plone-org please run jobs

To ensure that these changes do not break other parts of Plone, the Plone test suite matrix needs to pass, but it takes 30-60 min. Other CI checks are usually much faster and the Plone Jenkins resources are limited, so when done pushing changes and all other checks pass either start all Jenkins PR jobs yourself, or simply add the comment above in this PR to start all the jobs automatically.

Happy hacking!

[mauritsvanrees]

This has no effect on Jenkins, so those jobs do not need to run.

[mauritsvanrees]

I have released 7.8.2 with this.