refactor: Replace ParseHashStr with FromHex

No need to have two functions with different names that achieve the
exact same thing.

src/core_read.cpp

@@ -234,15 +234,6 @@ bool DecodeHexBlk(CBlock& block, const std::string& strHexBlk)
     return true;
 }
 
-bool ParseHashStr(const std::string& strHex, uint256& result)
-{
-    if ((strHex.size() != 64) || !IsHex(strHex))
-        return false;
-
-    result.SetHexDeprecated(strHex);
-    return true;
-}
-
 util::Result<int> SighashFromStr(const std::string& sighash)
 {
     static const std::map<std::string, int> map_sighash_values = {