Claude Instant 1.2 removed from LeMUR

The following models were removed from LeMUR: anthropic/claude-instant-1-2 and basic (legacy, equivalent to anthropic/claude-instant-1-2), which will now return a 400 validation error if called.

These models were removed due to Anthropic sunsetting legacy models in favor of newer models which are more performant, faster, and cheaper. We recommend users who were using the removed models switch to Claude 3 Haiku (anthropic/claude-3-haiku).