Accept any h2 version (#2444)

Alternatively we could bump this to 0.4.0, check for either 0.3.0 or
0.4.0, or do an extra explicit check for version >= 0.3.0 outside of
the find_package syntax.

CMakeLists.txt

@@ -243,7 +243,7 @@ endif ()
 
 # DiHydrogen and Distconv
 if (LBANN_WITH_DISTCONV)
-  find_package(DiHydrogen 0.3.0 CONFIG REQUIRED COMPONENTS Meta Patterns DistConv)
+  find_package(DiHydrogen CONFIG REQUIRED COMPONENTS Meta Patterns DistConv)
   set(LBANN_HAS_DISTCONV TRUE)
   set(LBANN_H2_LIBS
     H2::H2Meta