Update golang Docker tag to v1.21 (#949)

renovate[bot] · web-flow · commit 10c3900bf834 · 2023-08-11T14:33:14.000Z
Co-authored-by: renovate[bot] &lt;29139614+renovate[bot]@users.noreply.github.com&gt;
diff --git a/Dockerfile b/Dockerfile
@@ -1,5 +1,5 @@
 # Build the manager binary
-FROM golang:1.20 as builder
+FROM golang:1.21 as builder
 ARG TARGETOS
 ARG TARGETARCH
 
