[JIRAALIGN-1836] Lean Metrics - Lead Time graph: Y axis is time, graph says items

Issue Summary

Raised by Peggy Graham, and confirmed by Kyle Foreman on ALIGNSP-4884

The Y-axis description in the graph Lean Metrics- Lead Time is named "items" instead of "time"
The help for this is correct, it says::

Lead Time: Line graph displaying the rolling history of the average time it takes work items in the PI to be accepted. A work item's lead time is calculated as the time that passes between the date it is created, and the date it is moved to an Accepted state, plus 1 day.

Example:

An epic is created on July 7th and marked as Accepted on July 9th.
July 7 - July 9 = 2 days +1 = 3 day Lead Time.

Since it's showing you a 3 day lead time, the graph should say Days, as Cycle Time does.

Steps to Reproduce

1. Go to Work in Process page
2. Click on Lean Metrics - upper right corner
3. Scroll down to the Lead Time graph
4. Look at Y-axis, it says Items. (screenshot attached)

Expected Results

Y-axis should be named "Days"

Actual Results

Y-axis is named generically "item".

Workaround

N/A