icu: Remove unnecessary FULL_OPTIMIZATION_arm setting

icu: Remove unnecessary FULL_OPTIMIZATION_arm setting

This is distro policy and shouldn't be getting set by the recipe.  It was
added in commit 9b547ecf849b66aa883328fb6b26d9b412a4d2ec as a workaround
for gcc bug #37436, but the compiler bug was fixed more than four years
ago and the workaround is no longer required.

(From OE-Core rev: 05caf3417402df5c4f8f722830bfb896385cf9a5)

Signed-off-by: Phil Blundell <philb@gnu.org>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>