common: Remove duplicated call to a function.

* common/openpgp-oid.c (openpgp_oid_to_str): Remove duplicated call.

The removed function was already called. No memleak etc, though.

• Fixes-commit: 4a1558d0c7190cf13d35385e47291a7aa121be3e
• Signed-off-by: Werner Koch <wk@gnupg.org>