Update golang Docker tag to v1.20

This MR contains the following updates:

Package	Type	Update	Change
golang	stage	minor	1.19 -> 1.20

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Dockerfile

-FROM golang:1.19 AS gobuild
+FROM golang:1.20 AS gobuild
 COPY modsec_logger.go /src/modsec_logger.go
 WORKDIR /src
 RUN go build -tags netgo -o modsec_logger modsec_logger.go