[Search:Stateful:EnterpriseSearch:WorkplaceSearch:Sources:Synchronization:Frequency] Frequency time input boxes are missing form labels

[bhavyarm]

Description

The frequency time input boxes are missing form labels on the frequency page for time inputs. These labels are necessary for assistive technology to read this page and announce to the user that they can input time frequencies in here.

Preconditions
At least one organizational source has been added

Steps to reproduce

1. Click on workplace search - sources - on the source you have added
2. Click on details ->On details page click on sync frequency, Kibana opens frequency page under synchronization
3. Run axe-core through this page
4. Notice frequency input time boxes are missing form labels causing WCAG A violation (9 violations)

Kibana Version: 8.17.0-Snapshot

OS: OS X

Browser: Chrome latest

WCAG or Vendor Guidance (optional)
Understanding SC 4.1.2: Name, Role, Value (Level A)(https://www.w3.org/WAI/WCAG22/Understanding/name-role-value.html)

Related to: https://github.com/elastic/search-team/issues/8256

[elasticmachine]

Pinging @elastic/kibana-accessibility (Project:Accessibility)