fix: perform auth server metadata discovery fallbacks on any 4xx#1193

pcarleton merged 1 commit intomodelcontextprotocol:mainmodelcontextprotocol/python-sdk:mainfrom

LucaButBoring:fix/as-metadata-fallback-conditionsLucaButBoring/mcp-python-sdk:fix/as-metadata-fallback-conditionsCopy head branch name to clipboard