chore(telemetry): fixes namespace for span pointer metric (#11565)

This metric is currently generating invalid payloads and is being
dropped by the tracer-telemetry-intake service.

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- Title is accurate
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Co-authored-by: Rachel Yang <[email protected]>

ddtrace/_trace/telemetry.py

@@ -6,7 +6,7 @@
 
 def record_span_pointer_calculation(context: str, span_pointer_count: int) -> None:
     telemetry_writer.add_count_metric(
-        namespace="tracer",
+        namespace="tracers",
         name="span_pointer_calculation",
         value=1,
         tags=(("context", context), ("count", _span_pointer_count_to_tag(span_pointer_count))),
@@ -45,7 +45,7 @@ def record_span_pointer_calculation_issue(
         tags += additional_tags
 
     telemetry_writer.add_count_metric(
-        namespace="tracer",
+        namespace="tracers",
         name="span_pointer_calculation.issue",
         value=1,
         tags=tags,