doc: Save selection as filter option not described in Application groups

[prakarsh-dt]

💭 Description

• Save selection as filter option not described in Application groups.
• Saved Filters option not described in Application groups

Documentation page: https://docs.devtron.ai/usage/application-groups#accessing-application-groups

👀 Have you spent some time to check if this issue has been raised before?

• I checked and didn't find similar issue

🏢 Have you read the Code of Conduct?

• I have read the Code of Conduct

AB#8481

[ashokdevtron]

@prakarsh-dt, we already have a sub-section for that in the doc. Please check the below snapshots.