Remove dependabot (#210)

*Description of changes:*
Current dependabot configuration was scanning
[airflow_constraints.txt](https://github.com/aws/amazon-mwaa-docker-images/blob/main/images/airflow/2.10.3/etc/airflow_constraints.txt)
and
[mwaa_essential_constraints.txt](https://github.com/aws/amazon-mwaa-docker-images/blob/main/images/airflow/2.10.3/etc/mwaa_essential_constraints.txt).
It automatically generates pull requests (PRs) when new versions are
available.

We do not want to perform version upgrades on airflow dependencies as we
need exact versions of Python dependencies that are compatible with a
particular version of Apache Airflow. For MWAA essential dependencies,
we need a thorough mechanism to ensure those upgrades don't break any
functionality.

I have opened this
[issue-208](#208)
to add dependabot once those automated testing mechanisms are in place.
For now removing the configuration to reduce noise.

______
By submitting this pull request, I confirm that you can use, modify,
copy, and redistribute this contribution, under the terms of your
choice.

Co-authored-by: Vishal Vijayvargiya <[email protected]>

README.md

@@ -8,7 +8,7 @@ MWAA](https://aws.amazon.com/managed-workflows-for-apache-airflow/) uses to run
 You can also use it locally if you want to run a MWAA-like environment for testing, experimentation,
 and development purposes.
 
-Currently, Airflow v2.9.2 and v2.10.1 are supported. Future versions in parity with Amazon MWAA will be added as
+Currently, Airflow v2.9.2 and above are supported. Future versions in parity with Amazon MWAA will be added as
 well. _Notice, however, that we do not plan to support previous Airflow versions supported by MWAA._
 
 ## Using the Airflow Image