fix typo

Author: dustinvanbuskirk

Dockerfile

@@ -4,7 +4,7 @@ RUN apk update && apk add curl
 
 RUN curl -o kubectl1.15 -L https://storage.googleapis.com/kubernetes-release/release/v1.15.0/bin/linux/amd64/kubectl
 RUN curl -o kubectl1.14 -L https://storage.googleapis.com/kubernetes-release/release/v1.14.0/bin/linux/amd64/kubectl
-RUN curl -o kubectl1.14 -L https://storage.googleapis.com/kubernetes-release/release/v1.13.0/bin/linux/amd64/kubectl
+RUN curl -o kubectl1.13 -L https://storage.googleapis.com/kubernetes-release/release/v1.13.0/bin/linux/amd64/kubectl
 RUN curl -o kubectl1.12 -L https://storage.googleapis.com/kubernetes-release/release/v1.12.0/bin/linux/amd64/kubectl
 RUN curl -o kubectl1.10 -L https://storage.googleapis.com/kubernetes-release/release/v1.10.0/bin/linux/amd64/kubectl
 RUN curl -o kubectl1.6 -L https://storage.googleapis.com/kubernetes-release/release/v1.6.0/bin/linux/amd64/kubectl