all: use Go 1.14 for building in docker images (#2345)

### What
Use Go 1.14 for building in docker images.

### Why
We recently switched to building with Go 1.13 and 1.14 in #2325 and we should use the latest version for our builds.

exp/services/recoverysigner/docker/Dockerfile

@@ -1,4 +1,4 @@
-FROM golang:1.13-stretch as build
+FROM golang:1.14-stretch as build
 
 ADD . /src/recoverysigner
 WORKDIR /src/recoverysigner

exp/services/webauth/docker/Dockerfile

@@ -1,4 +1,4 @@
-FROM golang:1.13-stretch as build
+FROM golang:1.14-stretch as build
 
 ADD . /src/webauth
 WORKDIR /src/webauth

services/horizon/docker/Dockerfile

@@ -1,4 +1,4 @@
-FROM golang:1.13-stretch AS builder
+FROM golang:1.14-stretch AS builder
 
 WORKDIR /go/src/github.com/stellar/go
 COPY go.mod go.sum ./
@@ -13,4 +13,4 @@ RUN apt-get update && apt-get install -y --no-install-recommends ca-certificates
 
 COPY --from=builder /go/bin/horizon ./
 
-ENTRYPOINT ["./horizon"]
+ENTRYPOINT ["./horizon"]

services/keystore/docker/Dockerfile

@@ -1,4 +1,4 @@
-FROM golang:1.13-stretch as build
+FROM golang:1.14-stretch as build
 
 ADD . /src/keystore
 WORKDIR /src/keystore

services/ticker/docker/Dockerfile

@@ -1,4 +1,4 @@
-FROM golang:1.13-stretch as build
+FROM golang:1.14-stretch as build
 
 ADD . /src/ticker
 WORKDIR /src/ticker