[headerssetter] Remove "Limitations" section from README. (open-telem…

…etry#27465)

The docs for the `headers_setter` extension state that the
`from_context` config option does not work if the batch processor is
used. I believe this comment is out of date, because it seems that the
[PR](open-telemetry/opentelemetry-collector#7578)
linked to the
[issue](open-telemetry/opentelemetry-collector#4544)
has been merged. Note that I haven't tested that this actually works
with the header setter extension. Please let me know if you think
testing is necessary.

Co-authored-by: Juraci Paixão Kröhling <juraci@kroehling.de>

extension/headerssetterextension/README.md

@@ -88,15 +88,8 @@ service:
       exporters: [ loki ]
 ```
 
-## Limitations
-
-At the moment, it is not possible to use the `from_context` option to ge the
-header value if Collector's pipeline contains the batch processor. See [#4544].
-
-
 [alpha]: https://github.com/open-telemetry/opentelemetry-collector#alpha
 [contrib]: https://github.com/open-telemetry/opentelemetry-collector-releases/tree/main/distributions/otelcol-contrib
 [Mimir]: https://grafana.com/oss/mimir/
 [Tempo]: https://grafana.com/oss/tempo/
-[Loki]: https://grafana.com/oss/loki/
-[#4544]: https://github.com/open-telemetry/opentelemetry-collector/issues/4544
+[Loki]: https://grafana.com/oss/loki/