fix: keep newline before OTLP receiver block in collector config

[coder]

If you set grafana-agent.withOTLPReceiver: true, the collector config the chart renders is invalid River.

In _collector-config.tpl, the trailing -}} on {{- if $agent.withOTLPReceiver -}} also strips the newline that follows it. Together with the leading {{-, that glues the OTLP receiver onto the closing brace of prometheus.remote_write:

}otelcol.receiver.otlp "otlp_receiver" {

grafana-agent can't parse this:

$ AGENT_MODE=flow grafana-agent fmt config.river   # v0.40.3
config.river:486:2: expected TERMINATOR, got IDENT

The fix removes the trailing chomp, which keeps the newline.

Testing

I rendered helm template -f coder-observability/values.yaml on main and ran grafana-agent fmt (v0.40.3) on the collector config.river:

	withOTLPReceiver: false (default)	withOTLPReceiver: true
before	ok	fails (above)
after	ok, output byte-identical	ok

The default render doesn't change, so compiled/ doesn't either. helm lint --strict passes.

Needed for coder/dogfood#655, which turns on the OTLP receiver in dogfood. That PR also needs a chart release that includes this fix.