Remove lowercase normalization for `<name>` in `servlet.request.parameter.<name>`

[trask]

Comment says:

https://github.com/open-telemetry/opentelemetry-java-instrumentation/blob/9e8323ad9355408fb848eca575b21fa95635417c/instrumentation/servlet/servlet-common/library/src/main/java/io/opentelemetry/instrumentation/servlet/internal/ServletRequestParametersExtractor.java#L75-L77

but headers are case insensitive, while request parameter are not, so we shouldn't be normalizing these.

This is currently behind experimental configuration otel.instrumentation.servlet.experimental.capture-request-parameters, so ok to change now, or could defer to 3.0.