fix: pi/Dockerfile to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-DEBIAN11-GLIBC-5927133
- https://snyk.io/vuln/SNYK-DEBIAN11-GLIBC-5927133
- https://snyk.io/vuln/SNYK-DEBIAN11-GLIBC-5927133
- https://snyk.io/vuln/SNYK-DEBIAN11-GLIBC-5927133
- https://snyk.io/vuln/SNYK-DEBIAN11-NGHTTP2-5953384

pi/Dockerfile

@@ -1,4 +1,4 @@
-FROM golang:1.18 AS build
+FROM golang:1.21.7 AS build
 WORKDIR /sensors
 COPY go.mod ./
 COPY go.sum ./
@@ -7,7 +7,7 @@ RUN go mod verify
 COPY *.go ./
 RUN CGO_ENABLED=0 GOOS=linux go build -installsuffix cgo -tags=nomsgpack -a -o app .
 
-FROM golang:1.18
+FROM golang:1.21.7
 WORKDIR /app
 COPY --from=build /sensors/app ./app
 CMD ["./app"]