Cast copied text to string in share intent

Some apps expect a String and return an error when there's a
SpannableString in the EXTRA_TEXT instead. Cast to a string to
avoid this.

Bug: 238837981
Fix: 238837981
Test: manual (steps in bug -- the EditTextActivity creates a
SpannableString)

Change-Id: I543342acf2032dacd6d66281434079f43c6dc08e
1 file changed