Bump maven-site-plugin from 3.8.2 to 3.9.1

[dependabot-preview[bot]]

Bumps maven-site-plugin from 3.8.2 to 3.9.1.

Commits

• 854e6a0 [maven-release-plugin] prepare release maven-site-plugin-3.9.1
• ec954c8 [MSITE-856] - NullPointer on org.apache.maven.plugins.site.render.SiteMap.rel...
• d4160ab fix javadoc issues with JDK 8
• 963cbcb remove unused plugins
• da10917 remove enforce bytecode now inherited from maven-parent
• e033328 [MSITE-757] remove shading not used any more
• 5179a4d [MSITE-863] fix Maven < 3.6.1 compatibility issue
• 028119f Github Actions
• 77c7cff [MSITE-863] upgrade m-reporting-exec to show that MSHARED-921 is fixed
• 36b11f4 [MSITE-863] revert ae9c132, not caused by Java 7 but Maven 3.6.0-
• Additional commits viewable in compare view

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