chore(dep): remove go.mod wrongly introduced by cbae66e

[sylr]

Hi,

Projects using this lib and go mod can't upgrade to the last pre v2.0.0 version because of this:

s.rabot:~/go/src/github.com/prometheus/prometheus$ go get -u=patch ./...
go: github.com/googleapis/gax-go/v2 patch => v2.0.5
go: github.com/go-openapi/jsonreference patch => v0.19.3
go: golang.org/x/text patch => v0.3.2
go: github.com/golang/protobuf patch => v1.3.4
go: github.com/go-openapi/validate patch => v0.19.6
go: github.com/go-openapi/runtime patch => v0.19.11
go: github.com/go-openapi/errors patch => v0.19.3
go: github.com/go-openapi/jsonpointer patch => v0.17.2
go: github.com/go-openapi/analysis patch => v0.17.2
go: github.com/go-openapi/jsonpointer patch => v0.19.3
go: github.com/go-openapi/strfmt patch => v0.19.4
go: github.com/mattn/go-colorable patch => v0.1.6
go: gopkg.in/yaml.v2 patch => v2.2.8
go: github.com/Azure/go-autorest/autorest patch => v0.9.6
go: github.com/go-openapi/loads patch => v0.19.5
go: github.com/go-openapi/swag patch => v0.17.2
go: google.golang.org/grpc patch => v1.20.1
go: github.com/go-openapi/analysis patch => v0.19.10
go: github.com/go-openapi/loads patch => v0.17.2
go: github.com/go-openapi/spec patch => v0.19.6
go: github.com/hashicorp/golang-lru patch => v0.5.4
go: github.com/gogo/protobuf patch => v1.2.1
go: github.com/go-openapi/swag patch => v0.19.7
go: go.opencensus.io patch => v0.22.3
go: go.mongodb.org/mongo-driver patch => v1.1.4
go: github.com/mattn/go-isatty patch => v0.0.12
go: github.com/json-iterator/go patch => v1.1.9
go: google.golang.org/grpc patch => v1.27.1
go: github.com/go-openapi/spec patch => v0.17.2
go: google.golang.org/grpc patch => v1.19.1
go: github.com/PuerkitoBio/purell patch => v1.1.1
go: github.com/go-openapi/jsonreference patch => v0.17.2
go: github.com/mailru/easyjson patch => v0.7.1
go: go.mongodb.org/mongo-driver patch => v1.0.4
go: github.com/prometheus/procfs patch => v0.0.10
go: k8s.io/klog patch => v0.3.3
go: github.com/aws/aws-sdk-go patch => v1.29.14
go: github.com/influxdata/influxdb patch => v1.7.10
go: github.com/hashicorp/serf patch => v0.8.5
go: github.com/grpc-ecosystem/grpc-gateway patch => v1.9.6
go: github.com/cespare/xxhash/v2 patch => v2.1.1
go: github.com/go-openapi/errors patch => v0.17.2
go: gopkg.in/yaml.v2 patch => v2.0.0
go: github.com/prometheus/client_golang patch => v0.9.4
go: github.com/beorn7/perks patch => v1.0.1
go: github.com/go-openapi/strfmt patch => v0.17.2
go: github.com/pkg/errors patch => v0.8.1
go: github.com/golang/snappy patch => v0.0.1
go: google.golang.org/grpc patch => v1.21.4
go: google.golang.org/grpc patch => v1.22.3
go: google.golang.org/grpc patch => v1.23.1
go: go.opencensus.io patch => v0.20.2
go: google.golang.org/api patch => v0.3.2
go: github.com/aws/aws-sdk-go patch => v1.25.50
go: github.com/hashicorp/go-rootcerts patch => v1.0.2
go: github.com/davecgh/go-spew patch => v1.1.1
go: github.com/google/go-cmp patch => v0.3.1
go: github.com/aws/aws-sdk-go patch => v1.27.4
go: github.com/miekg/dns patch => v1.0.15
go: github.com/aws/aws-sdk-go patch => v1.15.90
go: google.golang.org/appengine patch => v1.6.5
go: cloud.google.com/go patch => v0.44.3
go get: github.com/influxdata/influxdb@v1.7.7 updating to
	github.com/influxdata/influxdb@v1.7.10 requires
	github.com/google/go-github@v0.0.0-20181009003523-dd29b543e14c: invalid version: go.mod has post-v0 module path "github.com/google/go-github/v18" at revision dd29b543e14c

Removing go.mod and the release of a v.1.7.11 tag should fix that.

Regards.

[williamhbaker]

Closing this PR since it is quite old and I assume any issues due to go.mod have been resolved in latest versions.