Fix typo in handbook/tools-and-tips/index.html.md

Why is this change being made?

Fix a missing letter in a recently added section of the handbook.

How will this merge request impact page speed?

Does this MR meet the acceptance criteria?

Assign to DRI

• Did you assign this change to the correct DRI of the page or information you are changing?

Conformity

• Added description to this MR explaining the reasons for the proposed change, per say-why-not-just-what