Remove duplicate colon in otherName display

The colon is already added in X509V3_EXT_val_prn(). In fact, the other
branches from i2v_GENERAL_NAME() do not include a trailing colon.

Reviewed-by: Tom Cosgrove <tom.cosgrove@arm.com>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/23428)