Bump CheckStyle version to 8.20.
<option name="configuration">
<map>
<entry key="active-configuration" value="LOCAL_FILE:$PROJECT_DIR$/etc/checkstyle-configuration.xml:Ullrich Hafner's CheckStyle Configuration" />
- <entry key="checkstyle-version" value="8.14" />
+ <entry key="checkstyle-version" value="8.20" />
<entry key="copy-libs" value="false" />
<entry key="location-0" value="BUNDLED:(bundled):Sun Checks" />
<entry key="location-1" value="BUNDLED:(bundled):Google Checks" />
