Remove redundant MerkleRoot function (#8733)

* Remove redundant MerkleRoot function

* update merle_tree() specs comment

shared/hashutil/BUILD.bazel

@@ -3,10 +3,7 @@ load("@io_bazel_rules_go//go:def.bzl", "go_test")
 
 go_library(
     name = "go_default_library",
-    srcs = [
-        "hash.go",
-        "merkleRoot.go",
-    ],
+    srcs = ["hash.go"],
     importpath = "github.com/prysmaticlabs/prysm/shared/hashutil",
     visibility = ["//visibility:public"],
     deps = [
@@ -22,10 +19,7 @@ go_library(
 go_test(
     name = "go_default_test",
     size = "small",
-    srcs = [
-        "hash_test.go",
-        "merkleRoot_test.go",
-    ],
+    srcs = ["hash_test.go"],
     deps = [
         ":go_default_library",
         "//proto/testing:go_default_library",

shared/trieutil/helpers.go

@@ -46,10 +46,15 @@ func PrevPowerOf2(n int) int {
 // MerkleTree returns all the nodes in a merkle tree from inputting merkle leaves.
 //
 // Spec pseudocode definition:
-//   def merkle_tree(leaves: Sequence[Hash]) -> Sequence[Hash]:
-//    padded_length = get_next_power_of_two(len(leaves))
-//    o = [Hash()] * padded_length + list(leaves) + [Hash()] * (padded_length - len(leaves))
-//    for i in range(padded_length - 1, 0, -1):
+//   def merkle_tree(leaves: Sequence[Bytes32]) -> Sequence[Bytes32]:
+//    """
+//    Return an array representing the tree nodes by generalized index:
+//    [0, 1, 2, 3, 4, 5, 6, 7], where each layer is a power of 2. The 0 index is ignored. The 1 index is the root.
+//    The result will be twice the size as the padded bottom layer for the input leaves.
+//    """
+//    bottom_length = get_power_of_two_ceil(len(leaves))
+//    o = [Bytes32()] * bottom_length + list(leaves) + [Bytes32()] * (bottom_length - len(leaves))
+//    for i in range(bottom_length - 1, 0, -1):
 //        o[i] = hash(o[i * 2] + o[i * 2 + 1])
 //    return o
 func MerkleTree(leaves [][]byte) [][]byte {