[exporter/clickhouse] Update README.md (#33732)

Updates metrics example queries to use current spec for `calls` (instead
of `calls_total`)

**Description:** <Describe what has changed.>
<!--Ex. Fixing a bug - Describe the bug and how this fixes the issue.
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exporter/clickhouseexporter/README.md

@@ -246,13 +246,13 @@ between Prometheus(OpenMetrics) and OTLP Metrics.
 - Find a sum metrics with name
 ```sql
 select TimeUnix,MetricName,Attributes,Value from otel_metrics_sum
-where MetricName='calls_total' limit 100
+where MetricName='calls' limit 100
 ```
 
 - Find a sum metrics with name, attribute.
 ```sql
 select TimeUnix,MetricName,Attributes,Value from otel_metrics_sum
-where MetricName='calls_total' and Attributes['service_name']='featureflagservice'
+where MetricName='calls' and Attributes['service_name']='featureflagservice'
 limit 100
 ```