package/icu: don't disable renaming for host build

Using a different renaming option for the icu host build can cause
issues for packages such as qt5webengine which expect target and
host packages to be built with the same options.

A package that needs both host and target to have the same options is most
probably doing somethig wrong, like linking a host program and taking the
result as valid for the target.

However, our adding the --disable-renaming in the first place in 3911e671
(icu: security bump to version 51.2) did not provide any explanations why it
was needed to begin with, so drop it.

Signed-off-by: James Hilliard <james.hilliard1@gmail.com>
Reviewed-by: Yann E. MORIN <yann.morin.1998@free.fr>
[Peter: extend commit message as suggested by Yann]
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>