remove jdk14 build from ci

[Tilman Hausherr]

I propose to remove the jdk14 build job. Reason: I think it's enough to 
keep the lowest (8) and the highest (17, I just changed it to 18) build, 
intermediate versions won't bring any surprises. Keeping jdk14 is a 
waste of energy.

Same argument for tika-branch1x-jdk11 .
Tilman