**Apache Airflow version**: 1.10.8 (Patched with latest AWS Hook)

**Environment**:

- **Cloud provider or hardware configuration**: 4 VCPU 8GB RAM VM
- **OS** (e.g. from /etc/os-release): RHEL 7.7
- **Kernel** (e.g. `uname -a`): Linux 3.10.0-957.el7.x86_64
- **Install tools**:
- **Others**:
The AWS Hook functionality for AssumeRoleWithSAML is not available in this version, we manually added it via patching the hook file.

**What happened**:
We've been using this hook for a while now with this issue, basically sts.assume_role and sts.assume_role_with_saml will return temporary credentials that are only valid for eg 1 hour by default. Eventually with long running operators / hooks / sensors some of them fail because the credentials have expired.

Example error messages
An error occurred (ExpiredTokenException) when calling the AssumeRole operation: Response has expired
An error occurred (ExpiredTokenException) when calling the AssumeRoleWithSAML operation: Response has expired
botocore.exceptions.ClientError: An error occurred (ExpiredTokenException) when calling the <any operation here> operation: The security token included in the request is expired

**What you expected to happen**:

AWS hook should be updated to use boto3 RefreshableCredentials when temporary credentials are in use.

**How to reproduce it**:

Use any of the assume role methods with the AWS Hook, create a session, wait 1 hour (or whatever expiry period applies to your role), and try and use the hook again.

**Anything else we need to know**:

I have a solution, please self-assign this.
airflow/providers/amazon/aws/hooks/base_aws.py
"""
        Get the underlying boto3 client/resource (cached)
        :return: boto3.client or boto3.resource
        :rtype: Union[boto3.client, boto3.resource]
        """
        if self.client_type:
            return self.get_client_type(self.client_type, region_name=self.region_name)
        elif self.resource_type:
            return self.get_resource_type(self.resource_type, region_name=self.region_name)
        else:
            
            raise NotImplementedError('Could not get boto3 connection!')
    def get_conn(self) -> Union[boto3.client, boto3.resource]:
        """
        Get the underlying boto3 client/resource (cached)
        Implemented so that caching works as intended. It exists for compatibility
        with subclasses that rely on a super().get_conn() method.
        :return: boto3.client or boto3.resource
        :rtype: Union[boto3.client, boto3.resource]
        """
        
        return self.conn
    def get_session(self, region_name: Optional[str] = None) -> boto3.session.Session: