[CALCITE-2570] Upgrade forbiddenapis to 2.6 for JDK 11 support
[CALCITE-2570] Upgrade forbiddenapis to 2.6 for JDK 11 support

Close apache/calcite-avatica#70

Signed-off-by: Kevin Risden <66e32a53aee277278658cf5d4b7ceaf23cd367ff@apache.org>

apache/calcite-avatica,apache/calcite-avatica,looker-open-source/calcite-avatica,apache/calcite-avatica,looker-open-source/calcite-avatica,looker-open-source/calcite-avatica,apache/calcite-avatica,apache/calcite-avatica,looker-open-source/calcite-avatica,looker-open-source/calcite-avatica