langchain: Make OutputFixingParser.from_llm() create a useable retry chain (#24687)
Description: OutputFixingParser.from_llm() creates a retry chain that
returns a Generation instance, when it should actually just return a
string.
Issue: https://github.com/langchain-ai/langchain/issues/24600
Twitter handle: scribu
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Co-authored-by: isaac hershenson <ihershenson@hmc.edu>