chore: silence otelsdk warnings across build paths (#105)

## Summary

Silences the recurring `OpenTelemetry error: there is no package called 'otelsdk'` warnings during builds.

## Root cause

The `build-env-*` images configure an OTel exporter (traces/logs/metrics), but `otelsdk` (the R OTel SDK backend) isn't installed. pak's `otel` instrumentation therefore tries to load `otelsdk` on every run and logs the error, falling back to a no-op.

`OTEL_SDK_DISABLED=true` (already set in `build-one.Dockerfile`) does **not** help — the R `otel` package ignores it and gates purely on `OTEL_R_<SIGNAL>_EXPORTER` (then the standard `OTEL_<SIGNAL>_EXPORTER`). When that resolves to a real exporter (`otlp`/`http`/…) with no SDK present, you get the error.

## Fix

Set `OTEL_R_TRACES_EXPORTER`, `OTEL_R_LOGS_EXPORTER`, and `OTEL_R_METRICS_EXPORTER` to `none` so the R otel providers are clean no-ops:

- `docker/build-one.Dockerfile` — exported alongside the existing OTel var.
- `.crow/process-updates.yaml`, `weekly-rebuild-missing.yaml`, `build-all-versions.yaml`, `build-all-versions-install-deps.yaml` — added to each step's `environment` block.

Using the R-specific variables (not the standard `OTEL_*_EXPORTER`) keeps OTel intact for any non-R tooling in the images.

Reviewed-on: #105

.crow/weekly-rebuild-missing.yaml

@@ -103,6 +103,9 @@ steps:
     image: reg.devxy.io/rpkgs/build-env-${IMG}
     pull: true
     environment:
+      OTEL_R_TRACES_EXPORTER: none
+      OTEL_R_LOGS_EXPORTER: none
+      OTEL_R_METRICS_EXPORTER: none
       RED_HAT_DEV_PW:
         from_secret: RED_HAT_DEV_PW
       B2_S3_ACCESS_KEY: