Update Dockerfiles using golang images to Go 1.16.13

Prior to this commit the Dockerfiles for windows images relied on an
older version of the official golang images.

This PR updates the windows images to use Go 1.16.13.

Author: Scott

images/windows/entrypoint/Dockerfile

@@ -1,6 +1,6 @@
 ARG BASE_IMAGE=mcr.microsoft.com/windows/nanoserver:1809
 
-FROM golang:1.16.4 AS builder
+FROM golang:1.16.13 AS builder
 
 COPY . c:/gopath/src/github.com/tektoncd/pipeline
 
@@ -20,4 +20,4 @@ COPY ./.git/refs c:/ProgramData/tektoncd/pipeline/data/refs/
 
 COPY ./third_party c:/ProgramData/tektoncd/pipeline/data/third-party/
 
-ENTRYPOINT ["c:/ko-app/entrypoint"]
+ENTRYPOINT ["c:/ko-app/entrypoint"]

images/windows/nop/Dockerfile

@@ -1,6 +1,6 @@
 ARG BASE_IMAGE=mcr.microsoft.com/windows/nanoserver:1809
 
-FROM golang:1.16.4 AS builder
+FROM golang:1.16.13 AS builder
 
 COPY . c:/gopath/src/github.com/tektoncd/pipeline
 
@@ -20,4 +20,4 @@ COPY ./.git/refs c:/ProgramData/tektoncd/pipeline/data/refs/
 
 COPY ./third_party c:/ProgramData/tektoncd/pipeline/data/third-party/
 
-ENTRYPOINT ["c:/ko-app/nop"]
+ENTRYPOINT ["c:/ko-app/nop"]