Update release markers when OpenJDK11 is GA

[SueChaplain]

References to Java 9 and 10
Where appropriate we should replace the icons that indicate changes for Java 9 and later or Java 10 and later with Java 11 and later, since this release supersedes 9 & 10.

Example page: https://www.eclipse.org/openj9/docs/xshareclasses/

[SueChaplain]

@DanHeidinga @mstoodle FYI - discussed this with @pshipton and we plan to do this work for the 0.10.0 release when 9 & 10 are effectively no longer supported.

[SueChaplain]

@DanHeidinga - similarly, as per your comment on #72, we will remove references to 9 and leave references to 10 until later.