Make AvroUtils compatible with older versions of Avro

[damccorm]

https://github.com/apache/beam/pull/32081#discussion_r1841033733 seems to have broken AvroUtils for Avro 1.8.2 - for example: https://github.com/apache/beam/actions/runs/11820539714

This fixes the problem by undoing that section of the pull request.

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[damccorm]

R: @Abacn

cc/ @tiglas @reuvenlax

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