[docs] Correct the exporter README section on data mutation (open-tel…

…emetry#7424)

* Correct the section about mutating data

* Typos

exporter/README.md

@@ -81,12 +81,10 @@ When multiple exporters are configured to send the same data (e.g. by configurin
 exporters for the same pipeline):
 * exporters *not* configured to mutate the data will have shared access to the data
 * exporters with the Capabilities to mutate the data will receive a copy of the data
+
 Exporters access export data when `ConsumeTraces`/`ConsumeMetrics`/`ConsumeLogs`
-function is called. Exporters MUST NOT modify the `pdata.Traces`/`pdata.Metrics`/`pdata.Logs` argument of
-these functions. If the exporter needs to modify the data while performing the exporting
-the exporter can clone the data and perform the modification on the clone or use a
-copy-on-write approach for individual sub-parts of `pdata.Traces`/`pdata.Metrics`/`pdata.Logs`.
-Any approach that does not mutate the original `pdata.Traces`/`pdata.Metrics`/`pdata.Logs` is allowed.
+function is called. Unless exporter's capabalities include mutation, the exporter MUST NOT modify the `pdata.Traces`/`pdata.Metrics`/`pdata.Logs` argument of
+these functions. Any approach that does not mutate the original `pdata.Traces`/`pdata.Metrics`/`pdata.Logs` is allowed without the mutation capability.
 
 ## Proxy Support
 
@@ -99,4 +97,4 @@ following proxy environment variables:
 - NO_PROXY
 
 If set at Collector start time then exporters, regardless of protocol,
-will or will not proxy traffic as defined by these environment variables.
+will or will not proxy traffic as defined by these environment variables.