Update Checkstyle to version 8.43

The checkstyle plugin in the 2021-03 version of Eclipse defaults to
version 8.43 of Checkstyle. This version of Checkstyle removes the
"scope" keyword from the JavadocMethod module, because it is redundant,
so the ONAP checkstyle onap-kava-style.xml file breaks.

This review:
- Removes the "scope" property from the "JavadocMethod" module, where it
  is redundant anyhow (scope applies on the "MissingJavadocMethod" module
- Removes the "scope" property from the "MissingJavadocMethod" because
  it defaults to the correct value for ONAP, that is "public"

Issue-ID: POLICY-3206
Change-Id: I62736ec812595929392b5eef0658acb77365c52a
Signed-off-by: liamfallon <liam.fallon@est.tech>