Bump Dockerfile dependencies

[cpaloukas]

I hit go.k6.io/xk6@v0.19.1 requires go >= 1.24.0 (running go 1.23.8) while trying to build the Dockerfile here: https://github.com/grafana/xk6-output-influxdb/blob/main/Dockerfile

Fixed it by bumping the builder base image to Go 1.26: FROM golang:1.26-alpine3.21 AS builder

[Brijeshthummar02]

@mstoykov should i open PR?

[Danyyer]

Opened PR #44 to fix this issue

[Brijeshthummar02]

@Danyyer there is already someone assigned you can not create PR without his concern.