Update module prometheus/client_golang to v1.6.0 (#463)

Update module prometheus/client_golang to v1.6.0

Reviewed-on: https://kolaente.dev/vikunja/api/pulls/463

vendor/google.golang.org/protobuf/internal/fieldnum/api_gen.go

@@ -0,0 +1,35 @@
+// Copyright 2019 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.
+
+// Code generated by generate-protos. DO NOT EDIT.
+
+package fieldnum
+
+// Field numbers for google.protobuf.Api.
+const (
+	Api_Name          = 1 // optional string
+	Api_Methods       = 2 // repeated google.protobuf.Method
+	Api_Options       = 3 // repeated google.protobuf.Option
+	Api_Version       = 4 // optional string
+	Api_SourceContext = 5 // optional google.protobuf.SourceContext
+	Api_Mixins        = 6 // repeated google.protobuf.Mixin
+	Api_Syntax        = 7 // optional google.protobuf.Syntax
+)
+
+// Field numbers for google.protobuf.Method.
+const (
+	Method_Name              = 1 // optional string
+	Method_RequestTypeUrl    = 2 // optional string
+	Method_RequestStreaming  = 3 // optional bool
+	Method_ResponseTypeUrl   = 4 // optional string
+	Method_ResponseStreaming = 5 // optional bool
+	Method_Options           = 6 // repeated google.protobuf.Option
+	Method_Syntax            = 7 // optional google.protobuf.Syntax
+)
+
+// Field numbers for google.protobuf.Mixin.
+const (
+	Mixin_Name = 1 // optional string
+	Mixin_Root = 2 // optional string
+)