Fix unexpanded macro warnings
    
    warning: line 73: Possible unexpanded macro in: Obsoletes:      libgda-java-devel < %{libgda4_obsoletes_version}
    warning: line 74: Possible unexpanded macro in: Obsoletes:      libgda-ldap-devel < %{libgda4_obsoletes_version}
    warning: line 75: Possible unexpanded macro in: Obsoletes:      libgda-mdb-devel < %{libgda4_obsoletes_version}
    warning: line 76: Possible unexpanded macro in: Obsoletes:      libgda-mysql-devel < %{libgda4_obsoletes_version}
    warning: line 77: Possible unexpanded macro in: Obsoletes:      libgda-postgres-devel < %{libgda4_obsoletes_version}
    warning: line 78: Possible unexpanded macro in: Obsoletes:      libgda-sqlcipher-devel < %{libgda4_obsoletes_version}
    warning: line 79: Possible unexpanded macro in: Obsoletes:      libgda-sqlite-devel < %{libgda4_obsoletes_version}
    warning: line 80: Possible unexpanded macro in: Obsoletes:      libgda-web-devel < %{libgda4_obsoletes_version}
    
    This commit drops the old obsoletes as they are no longer needed.