Fix building documentation for PSRP (#21260)
Fix building documentation for PSRP (#21260)

The PSRP docs building fails in main/commiter PRs after 
merging #19806 because the documentation needs to be 
rebuilt one more time. In parallel builds,  sequence of building
 the documentation matters. In main and the commiter PRs 
the "apache-airflow" documentation does not complete build
before misrosoft psrp is built, and the psrp docs uses
reference to the airlfow "concept" documentation and the
link is not existing yet in the inventory for apache-airflow.
This results in a race condition where PSRP documentation fails
with `toctree contains reference to nonexisting document`

The error has not been included in the list of errors that
are "eligible for rebuild" and the race condition was triggered.

This change adds the error to errors "eligible for rebuild" and
makes PSRP documentation build succeed on retry.
nathanielvarona/airflow,Acehaidrey/incubator-airflow,apache/airflow,bolkedebruin/airflow,bolkedebruin/airflow,cfei18/incubator-airflow,bolkedebruin/airflow,apache/airflow,lyft/incubator-airflow,danielvdende/incubator-airflow,nathanielvarona/airflow,Acehaidrey/incubator-airflow,Acehaidrey/incubator-airflow,danielvdende/incubator-airflow,apache/airflow,apache/airflow,danielvdende/incubator-airflow,Acehaidrey/incubator-airflow,bolkedebruin/airflow,lyft/incubator-airflow,cfei18/incubator-airflow,apache/airflow,nathanielvarona/airflow,lyft/incubator-airflow,Acehaidrey/incubator-airflow,danielvdende/incubator-airflow,nathanielvarona/airflow,Acehaidrey/incubator-airflow,danielvdende/incubator-airflow,apache/airflow,danielvdende/incubator-airflow,nathanielvarona/airflow,cfei18/incubator-airflow,cfei18/incubator-airflow,lyft/incubator-airflow,cfei18/incubator-airflow,cfei18/incubator-airflow,nathanielvarona/airflow,bolkedebruin/airflow