[8] RFR: Fix tier2_gc_shenandoah group definition

[Roman Kennke]

Uff. Ok, that makes sense.

Roman


> A trivial thing that happened back in 2018 during test configs backports:
> 
> diff -r 7f027e9c4a4b test/TEST.groups
> --- a/test/TEST.groups  Fri Feb 28 17:59:50 2020 +0100
> +++ b/test/TEST.groups  Mon Mar 02 11:18:21 2020 +0100
> @@ -150,5 +150,5 @@
>    gc/startup_warnings/TestShenandoah.java \
>    gc/shenandoah/jvmti/TestGetLoadedClasses.sh \
> -  gc/shenandoah/
> +  gc/shenandoah/ \
>    -gc/shenandoah/TestStringDedupStress.java \
>    -gc/shenandoah/jni/TestCriticalNativeStress.sh \
> 
> Missing backslash makes jtreg ignore the rest of the block, and print the warning message.
> 
> 11u has it right, jdk/jdk has it right, but not 8u.
> 
> Testing: hotspot_gc_shenandoah
>