bump to latest collector version (#4448)

Author: jaronoff97

versions.txt

@@ -2,7 +2,7 @@
 # by default with the OpenTelemetry Operator. This would usually be the latest
 # stable OpenTelemetry version. When you update this file, make sure to update the
 # the docs as well.
-opentelemetry-collector=0.137.0
+opentelemetry-collector=0.138.0
 
 # Represents the current release of the OpenTelemetry Operator.
 operator=0.137.0