docs: fix review issues in registry and collector docs

- GCCollector does not support registry=None on CPython; remove that claim
- Remove unused CONTENT_TYPE_LATEST import from registry example
- Fix 'value vs labels' section to correctly describe Summary (count_value/sum_value) and Histogram (buckets)

Signed-off-by: k1chik <107162115+k1chik@users.noreply.github.com>

Author: k1chik

docs/content/collector/_index.md

@@ -94,7 +94,7 @@ other implementations).
 
 | Parameter | Type | Default | Description |
 |-----------|------|---------|-------------|
-| `registry` | `CollectorRegistry` | `REGISTRY` | Registry to register with. Pass `None` to skip registration. |
+| `registry` | `CollectorRegistry` | `REGISTRY` | Registry to register with. |
 
 Metrics exported:
 

docs/content/collector/custom.md

@@ -56,11 +56,11 @@ at registration time instead.
 
 ## value vs labels
 
-Every metric family constructor accepts either `value` or `labels`, but not
-both.
+Every metric family constructor accepts either inline data or `labels`, but not
+both. The inline data parameter name varies by type: `value` for Gauge, Counter,
+and Info; `count_value`/`sum_value` for Summary; `buckets` for Histogram.
 
-- Pass `value` (and for counters, optionally `created`) to emit a single
-  unlabelled metric directly from the constructor.
+- Pass inline data to emit a single unlabelled metric directly from the constructor.
 - Pass `labels` (a sequence of label names) and then call `add_metric` one or
   more times to emit labelled metrics.
 

docs/content/registry/_index.md

@@ -74,7 +74,7 @@ for partial scrapes. See [Restricted registry](../restricted-registry/) for
 usage with `generate_latest` and the built-in HTTP server.
 
 ```python
-from prometheus_client import generate_latest, CONTENT_TYPE_LATEST
+from prometheus_client import generate_latest
 
 subset = REGISTRY.restricted_registry(['python_info', 'process_cpu_seconds_total'])
 output = generate_latest(subset)