RFR: JMC-6561: update Eclipse 4.11 in Prerequisites of update site landing page

[Guru]

Hi,

Please review the fix for 
JBS : https://bugs.openjdk.java.net/browse/JMC-6561 <https://bugs.openjdk.java.net/browse/JMC-6561>
webrev : http://cr.openjdk.java.net/~ghb/JMC-6561/webrev.0/ <http://cr.openjdk.java.net/~ghb/JMC-6561/webrev.0/> 

Root cause : JMC 7.0.0 is compiled and shipped with Eclipse 4.11 (2019-03 as default profile) where as update sites landing page still refers to Eclipse 4.7 and above as Prerequisite. 
Solution : Updated Eclipse version from 4.7 to 4.8 in the Prerequisite description in the landing page. 

Note: This fix will be applicable to jmc7 repo only (i.e. for Jmc 7.0.0 release). 

Thanks,
Guru