Update required JDK version in README (#1749)
Update required JDK version in README (#1749)

Signed-off-by: Sylvain Leclerc <5d993eb81f6b79378b255a42c1e36c7b95012258@rte-france.com>
powsybl/powsybl-core,powsybl/powsybl-core,powsybl/powsybl-core