Update help content for the rule input_onchange_review

[shunguoy]

see the rule issue #1624
see the rule discussion result: https://ibm.ent.box.com/notes/1552679742378

[shunguoy]

branch: dev-1624
PP: #1928

[philljenkins]

implementing Help changes per the rule discussion: https://ibm.ent.box.com/notes/1552679742378

[philljenkins]

Previous rule messages were:

input_onchange_review: Verify that any changes of context are explained in advance to the user
Needs review

• Verify that any changes of context are explained in advance to the user

after implementation rule messages are:

input_onchange_review: Users must be advised if, due to a change of element value, a form automatically submits, a new window opens, or a change in focus occurs
Needs review

• Confirm that the user is advised if, due to a change of element value, a form automatically submits, a new window opens, or a change in focus occurs

[philljenkins]

Help changes made per rule discussion note:

Before:

After:

[philljenkins]

@shunguoy can you review the Help changes for technical accuracy, then we can move the PR to Review.