Clarify overflow attribute description in doc.go to indicate it is boolean true (#7247)

and not string "true"

---------

Co-authored-by: Robert Pająk <[email protected]>
Co-authored-by: Damien Mathieu <[email protected]>

Author: 3 people

sdk/metric/doc.go

@@ -50,7 +50,7 @@
 //
 // New attribute sets are dropped when the cardinality limit is reached. The measurement of
 // these sets are aggregated into
-// a special attribute set containing "otel.metric.overflow" attribute with "true" value.
+// a special attribute set containing attribute.Bool("otel.metric.overflow", true).
 // This ensures total metric values (e.g., Sum, Count) remain correct for the
 // collection cycle, but information about the specific dropped sets
 // is not preserved.