Update download URL for ocb

[jpkrohling]

ocb has its own tag now on the core repository, causing the download URL to change. This PR makes the Makefile use the new location.

When ocb is not on the path, the following happens:

> make generate-sources
Installing ocb (linux/amd64) at /home/jpkroehling/bin
Skipping the compilation, we'll only generate the sources.
Distributions to build: sidecar,tracing,otel-grafana
Building: sidecar
Using Builder: /home/jpkroehling/bin/ocb
Using Go: /usr/bin/go
❌ ERROR: failed to build the distribution 'sidecar'.
🪵 Build logs for 'sidecar'
----------------------
/home/jpkroehling/bin/ocb: line 1: Not: command not found
----------------------
make: *** [Makefile:24: generate-sources] Error 1

After this change:

> make generate-sources
Installing ocb (linux/amd64) at /home/jpkroehling/bin
Skipping the compilation, we'll only generate the sources.
Distributions to build: sidecar,tracing,otel-grafana
Building: sidecar
Using Builder: /home/jpkroehling/bin/ocb
Using Go: /usr/bin/go
✅ SUCCESS: distribution 'sidecar' built.
Building: tracing
Using Builder: /home/jpkroehling/bin/ocb
Using Go: /usr/bin/go
✅ SUCCESS: distribution 'tracing' built.
Building: otel-grafana
Using Builder: /home/jpkroehling/bin/ocb
Using Go: /usr/bin/go
✅ SUCCESS: distribution 'otel-grafana' built.

Signed-off-by: Juraci Paixão Kröhling juraci@kroehling.de

[jpkrohling]

@rlankfo, would you like to review this one?

[rlankfo]

LGTM