Revert "Add contract spec type for hash (#182)" (#184)

This reverts commit 2ba4049.

Author: leighmcculloch

Stellar-contract-spec.x

@@ -42,7 +42,6 @@ enum SCSpecType
     SC_SPEC_TYPE_MAP = 1004,
     SC_SPEC_TYPE_TUPLE = 1005,
     SC_SPEC_TYPE_BYTES_N = 1006,
-    SC_SPEC_TYPE_HASH = 1007,
 
     // User defined types.
     SC_SPEC_TYPE_UDT = 2000
@@ -80,11 +79,6 @@ struct SCSpecTypeBytesN
     uint32 n;
 };
 
-struct SCSpectTypeHash
-{
-    uint32 n;
-};
-
 struct SCSpecTypeUDT
 {
     string name<60>;
@@ -123,8 +117,6 @@ case SC_SPEC_TYPE_TUPLE:
     SCSpecTypeTuple tuple;
 case SC_SPEC_TYPE_BYTES_N:
     SCSpecTypeBytesN bytesN;
-case SC_SPEC_TYPE_HASH:
-    SCSpectTypeHash hash;
 case SC_SPEC_TYPE_UDT:
     SCSpecTypeUDT udt;
 };