[connector/servicegraphconnector] Fix collect Client latency metrics bug (#39184)

<!--Ex. Fixing a bug - Describe the bug and how this fixes the issue.
Ex. Adding a feature - Explain what this achieves.-->
#### Description
fix `collectClientLatencyMetrics` method bug.

The `collectClientLatencyMetrics` method need to loop
`reqClientDurationSecondsCount` var instead of
`reqServerDurationSecondsCount`.

Author: Frapschen

.chloggen/fix-servicegraph-bug.yaml

@@ -0,0 +1,27 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: bug_fix
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: servicegraphconnector
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Fix collectClientLatencyMetrics method bug
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [39184]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: [user]

connector/servicegraphconnector/connector.go

@@ -546,7 +546,7 @@ func (p *serviceGraphConnector) collectLatencyMetrics(ilm pmetric.ScopeMetrics)
 }
 
 func (p *serviceGraphConnector) collectClientLatencyMetrics(ilm pmetric.ScopeMetrics) error {
-	if len(p.reqServerDurationSecondsCount) > 0 {
+	if len(p.reqClientDurationSecondsCount) > 0 {
 		mDuration := ilm.Metrics().AppendEmpty()
 		mDuration.SetName("traces_service_graph_request_client")
 		mDuration.SetUnit(secondsUnit)
@@ -557,7 +557,7 @@ func (p *serviceGraphConnector) collectClientLatencyMetrics(ilm pmetric.ScopeMet
 		mDuration.SetEmptyHistogram().SetAggregationTemporality(pmetric.AggregationTemporalityCumulative)
 		timestamp := pcommon.NewTimestampFromTime(time.Now())
 
-		for key := range p.reqServerDurationSecondsCount {
+		for key := range p.reqClientDurationSecondsCount {
 			dpDuration := mDuration.Histogram().DataPoints().AppendEmpty()
 			dpDuration.SetStartTimestamp(pcommon.NewTimestampFromTime(p.startTime))
 			dpDuration.SetTimestamp(timestamp)