TNZ-66733 - Update 10.3 docs to add language on customer rate limiting performance

[nookala]

Update docs with the language

[anita-flegg]

@nookala , The text for this PR says 10.3, but you've added it to the 10.4 branch.
Do you want the update in both 10.3 and 10.4, or only 10.4?

[nookala]

@nookala , The text for this PR says 10.3, but you've added it to the 10.4 branch. Do you want the update in both 10.3 and 10.4, or only 10.4?

I'm assuming it goes into both, but will confirm with product.

[anita-flegg]

@nookala , please confirm branches or close PR. Thanks!