debian/libgrokj2k1.symbols: remove debian revision from symbols versions

Debian revisions should be stripped from versions in symbols files.

Not doing so leads to dependencies unsatisfiable by backports (1.0-1~bpo
<< 1.0-1 while 1.0-1~bpo >= 1.0).

This fixes the following lintian error:

E: libgrokj2k1: symbols-file-contains-current-version-with-debian-revision on symbol _ZNKSt13__future_base13_State_baseV221_M_is_deferred_futureEv@Base and 351 others