Increased the number of rows in AbuseFilter's Filter testing textarea

Changed the textarea size in AbuseFilter Notes text area
from 5 to 15 to match with the new Conditions text box.

Bug: 55365
Change-Id: I1da26166f28f31b2a18c1dca3709efc0728d45d6
Merge "Increased the number of rows in AbuseFilter's Filter testing textarea"