Bump jsonschema from 3.2.0 to 4.4.0

The big breaking change for our code (not mentioned in the changelog) is
that the built-in validator for the `date-time` format now requires the
`rfc3339-validator` package instead of the `strict-rfc3339` package.
This updates the requirements file to use `rfc3339-validator`. Without
this change, wrong `date-time` formats would always silently pass validation.

requirements.txt

@@ -123,7 +123,7 @@ jmespath==0.10.0
     # via
     #   boto3
     #   botocore
-jsonschema==3.2.0
+jsonschema==4.4.0
     # via -r requirements.in
 kombu==5.2.3
     # via celery
@@ -200,6 +200,8 @@ requests==2.26.0
     #   govuk-bank-holidays
     #   notifications-python-client
     #   notifications-utils
+rfc3339-validator==0.1.4
+    # via -r requirements.in
 rfc3987==1.3.8
     # via -r requirements.in
 rsa==4.7.2
@@ -218,8 +220,8 @@ six==1.16.0
     #   click-repl
     #   eventlet
     #   flask-marshmallow
-    #   jsonschema
     #   python-dateutil
+    #   rfc3339-validator
 smartypants==2.0.1
     # via notifications-utils
 soupsieve==2.2.1
@@ -231,8 +233,6 @@ sqlalchemy==1.4.35
     #   marshmallow-sqlalchemy
 statsd==3.3.0
     # via notifications-utils
-strict-rfc3339==0.7
-    # via -r requirements.in
 urllib3==1.26.7
     # via
     #   botocore