Change Job Template Skip Tags character limit to align with Job Tags character limit

1. What is the nature and description of the request?

On a job template, the Job Tags and Skips Tags have a similar (but opposite) functionality. They either include or exclude tasks in a playbook. The input fields also look and react alike, until the input exceeds 1024 chars.

The Job Tags field is a TextField, where the Skip Tags field is a CharField, which a char limit of 1024. These should both be the same type of field. 

2. Why does the customer need this? (List the business requirements here)

If there is a playbook with many tasks, and many of those tasks need to be skipped, the field limits the amount of tags that can be applied by limiting the number of characters.

Also, the customer would expect these two fields to function similarly, since they seem to behave similarly. 

3. How would you like to achieve this? (List the functional requirements here)

Modify the type of field the Skip Tags is to align with Job Tags field

4. List any affected known dependencies: Doc, UI etc..

None

5. Github Link if any

https://github.com/ansible/tower/blob/ae7be2eea1521aa40c6cd019c81c14bb1497ac60/awx/main/models/jobs.py#L135

The above should be changed from:

    skip_tags = models.CharField(
        max_length=1024,
        blank=True,
        default='',
    )

to:

    skip_tags = models.TextField(
        blank=True,
        default='',
    )