requirements: Add pointer to fix for openapi-core

This will be fixed in a future openapi-core release [1]. Indicate as
much.

[1] python-openapi/openapi-core#373

Signed-off-by: Stephen Finucane <[email protected]>

Author: stephenfin

requirements-test.txt

@@ -6,7 +6,8 @@ tblib~=1.7.0
 openapi-core~=0.14.2
 # FIXME(stephenfin): We have to pin this to prevent a recurrence of [1]. It
 # seems openapi-core needs to gain support for OpenAPI 3.1 before we can fix
-# this properly
+# this properly [2]
 #
 # [1] https://github.com/OAI/OpenAPI-Specification/issues/1368
+# [2] https://github.com/p1c2u/openapi-core/pull/373
 jsonschema<4.0