opentelemetry-sdk: merge doesn't need a copy, dict already does this (#5326)

* opentelemetry-sdk: merge doesn't need a copy, dict already does this

Removing a call to .copy() in the merge function as it is unnecessary.

Signed-off-by: Alex Boten <223565+codeboten@users.noreply.github.com>

* changelog

Signed-off-by: Alex Boten <223565+codeboten@users.noreply.github.com>

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Signed-off-by: Alex Boten <223565+codeboten@users.noreply.github.com>
Co-authored-by: Riccardo Magliocchetti <riccardo.magliocchetti@gmail.com>