Fix link to Release 20
Fix link to Release 20

Also remove the no-longer-needed link to v20-rc1.
Xaerxess/guava,typetools/guava,rgoldberg/guava,mosoft521/guava,DavesMan/guava,Xaerxess/guava,xasx/guava,tli2/guava,mosoft521/guava,google/guava,typetools/guava,tli2/guava,berndhopp/guava,EdwardLee03/guava,mosoft521/guava,berndhopp/guava,DavesMan/guava,xasx/guava,google/guava,google/guava,rgoldberg/guava,EdwardLee03/guava