[8u] RFR: Prune unneeded (jccb|jmpb)_if_possible

[Roman Kennke]

Ok, thanks!

Roman


> http://cr.openjdk.java.net/~shade/shenandoah/prune-if-possible/webrev.01/
> 
> This shows up as difference against 8u upstream. But this is not really needed, and we have actually
> purged it in all other versions. See here:
>   https://mail.openjdk.java.net/pipermail/shenandoah-dev/2018-June/006287.html
> 
> Testing: hotspot_gc_shenandoah
>