mpich: Remove incorrect dependency (#47586)

The gni libfabric provider works on some Cray systems, but not all. For
example, Slingshot-based machines use a different libfabric provider
(cxi). Therefore libfabric/gni should not be a dependency when using
Cray PMI.

var/spack/repos/builtin/packages/mpich/package.py

@@ -262,7 +262,6 @@ class Mpich(AutotoolsPackage, CudaPackage, ROCmPackage):
     depends_on("hwloc@2.0.0:", when="@3.3: +hwloc")
 
     depends_on("libfabric", when="netmod=ofi")
-    depends_on("libfabric fabrics=gni", when="netmod=ofi pmi=cray")
     # The ch3 ofi netmod results in crashes with libfabric 1.7
     # See https://github.com/pmodels/mpich/issues/3665
     depends_on("libfabric@:1.6", when="device=ch3 netmod=ofi")