Remove unused QueryRendererBuilder locals in JPQL and HQL query renderers

[jewoodev]

While following up on #4273, I found two leftover QueryRendererBuilder locals that are never used.

This removes the unused builder in JpqlQueryRenderer#visitString_expression and the empty nested builder plus no-op appendInline(nested) in HqlQueryRenderer#visitListaggFunction. Rendering behavior is unchanged.

Verified with the JPQL/HQL/EQL renderer round-trip suites.

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