Fix hiding the 'say' bubble WRT number formatting

When setting bubble text, numbers are rounded to two decimal places if
necessary. The check before hiding the bubble that makes sure the
current bubble text matches the current value -- probably intended to
make sure it's "our" bubble -- now uses the same text formatting code to
avoid false negatives.
"We might use it later" is not a good reason to add something now. If we ever need to set the source for app bubbles, we can make that change when we need it.