all: Update seriesmeta golang-crossbuild image to 1.16.6

Author: pgaskin

.github/workflows/kepubify.yml

@@ -126,19 +126,19 @@ jobs:
          uses: "docker://golang:1.17-rc-alpine", with: {entrypoint: go, args: "build -v -ldflags \"-s -w -X main.version=${{steps.version.outputs.version}}\" -trimpath -o ./build/covergen-windows-arm64.exe ./cmd/covergen"}, env: {CGO_ENABLED: 0, GOOS: windows, GOARCH: arm64}}
 
       - {name: Build - seriesmeta-linux-64bit,
-         uses: "docker://docker.elastic.co/beats-dev/golang-crossbuild:1.16.4-main", with: {entrypoint: /crossbuild,
+         uses: "docker://docker.elastic.co/beats-dev/golang-crossbuild:1.16.6-main", with: {entrypoint: /crossbuild,
          args: "--platforms linux/amd64 --build-cmd \"CGO_ENABLED=0 go build -v -ldflags '-s -w -X main.version=${{steps.version.outputs.version}}' -trimpath -o ./build/seriesmeta-linux-64bit ./cmd/seriesmeta\""}}
       - {name: Build - seriesmeta-linux-arm,
-         uses: "docker://docker.elastic.co/beats-dev/golang-crossbuild:1.16.4-armhf", with: {entrypoint: /crossbuild,
+         uses: "docker://docker.elastic.co/beats-dev/golang-crossbuild:1.16.6-armhf", with: {entrypoint: /crossbuild,
          args: "--platforms linux/armv7 --build-cmd \"CGO_ENABLED=0 go build -v -ldflags '-s -w -X main.version=${{steps.version.outputs.version}}' -trimpath -o ./build/seriesmeta-linux-arm ./cmd/seriesmeta\""}}
       - {name: Build - seriesmeta-linux-arm64,
-         uses: "docker://docker.elastic.co/beats-dev/golang-crossbuild:1.16.4-arm", with: {entrypoint: /crossbuild,
+         uses: "docker://docker.elastic.co/beats-dev/golang-crossbuild:1.16.6-arm", with: {entrypoint: /crossbuild,
          args: "--platforms linux/arm64 --build-cmd \"CGO_ENABLED=0 go build -v -ldflags '-s -w -X main.version=${{steps.version.outputs.version}}' -trimpath -o ./build/seriesmeta-linux-arm64 ./cmd/seriesmeta\""}}
       - {name: Build - seriesmeta-darwin-64bit,
-         uses: "docker://docker.elastic.co/beats-dev/golang-crossbuild:1.16.4-darwin", with: {entrypoint: /crossbuild,
+         uses: "docker://docker.elastic.co/beats-dev/golang-crossbuild:1.16.6-darwin", with: {entrypoint: /crossbuild,
          args: "--platforms darwin/amd64 --build-cmd \"CGO_ENABLED=0 go build -v -ldflags '-s -w -X main.version=${{steps.version.outputs.version}}' -trimpath -o ./build/seriesmeta-darwin-64bit ./cmd/seriesmeta\""}}
       - {name: Build - seriesmeta-windows-64bit.exe,
-         uses: "docker://docker.elastic.co/beats-dev/golang-crossbuild:1.16.4-main", with: {entrypoint: /crossbuild,
+         uses: "docker://docker.elastic.co/beats-dev/golang-crossbuild:1.16.6-main", with: {entrypoint: /crossbuild,
          args: "--platforms windows/amd64 --build-cmd \"CGO_ENABLED=0 go build -v -ldflags '-s -w -X main.version=${{steps.version.outputs.version}}' -trimpath -o ./build/seriesmeta-windows-64bit.exe ./cmd/seriesmeta\""}}
 
       - name: List