[connector/signaltometrics]Fix typo for AdjustedCount in README (open-telemetry#38642)

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

Fixes a typo in custom OTTL func name.

<!-- Issue number (e.g. open-telemetry#1234) or full URL to issue, if applicable. -->
#### Link to tracking issue
Raised in
open-telemetry#38640 (comment)

<!--Describe what testing was performed and which tests were added.-->
#### Testing

N/A

<!--Describe the documentation added.-->
#### Documentation

N/A
<!--Please delete paragraphs that you did not use before submitting.-->

Author: lahsivjar

connector/signaltometricsconnector/README.md

@@ -42,7 +42,7 @@ signaltometrics:
     - name: span.count
       description: Count of spans
       sum:
-        value: Int(AbsoluteCount()) # Count of total spans represented by each span
+        value: Int(AdjustedCount()) # Count of total spans represented by each span
   datapoints:
     - name: datapoint.count
       description: Count of datapoints