Remove chat agent all models logic (microsoft#252459)

Remove unused chat.agent.allModels configuration. No longer useful and tends to confuse people.

Author: roblourens

src/vs/workbench/contrib/chat/browser/chatInputPart.ts

@@ -558,10 +558,6 @@ export class ChatInputPart extends Disposable implements IHistoryNavigationWidge
 	private modelSupportedForDefaultAgent(model: ILanguageModelChatMetadataAndIdentifier): boolean {
 		// Probably this logic could live in configuration on the agent, or somewhere else, if it gets more complex
 		if (this.currentMode === ChatMode.Agent || (this.currentMode === ChatMode.Edit && this.configurationService.getValue(ChatConfiguration.Edits2Enabled))) {
-			if (this.configurationService.getValue('chat.agent.allModels')) {
-				return true;
-			}
-
 			const supportsToolsAgent = typeof model.metadata.capabilities?.agentMode === 'undefined' || model.metadata.capabilities.agentMode;
 
 			// Filter out models that don't support tool calling, and models that don't support enough context to have a good experience with the tools agent