Remove replace directives and use own fork to make go get work again (#1028)

See https://github.com/golang/go/issues/30354
go get doesn't honor the go.mod replace options.

vendor/github.com/yaegashi/msgraph.go/jsonx/tags.go

@@ -1,44 +0,0 @@
-// Copyright 2011 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package jsonx
-
-import (
-	"strings"
-)
-
-// tagOptions is the string following a comma in a struct field's "json"
-// tag, or the empty string. It does not include the leading comma.
-type tagOptions string
-
-// parseTag splits a struct field's json tag into its name and
-// comma-separated options.
-func parseTag(tag string) (string, tagOptions) {
-	if idx := strings.Index(tag, ","); idx != -1 {
-		return tag[:idx], tagOptions(tag[idx+1:])
-	}
-	return tag, tagOptions("")
-}
-
-// Contains reports whether a comma-separated list of options
-// contains a particular substr flag. substr must be surrounded by a
-// string boundary or commas.
-func (o tagOptions) Contains(optionName string) bool {
-	if len(o) == 0 {
-		return false
-	}
-	s := string(o)
-	for s != "" {
-		var next string
-		i := strings.Index(s, ",")
-		if i >= 0 {
-			s, next = s[:i], s[i+1:]
-		}
-		if s == optionName {
-			return true
-		}
-		s = next
-	}
-	return false
-}