Do not self-dispose

stumbled over https://github.com/microsoft/vscode/blob/dac0c97d082bd3bf38fdb3251e955e25c7c992a0/src/vs/workbench/contrib/chat/common/promptSyntax/contributions/languageFeatures/providers/providerInstanceBase.ts#L43


It seems `ProviderInstanceBase`-instances dispose themselves when their `parser`-property gets disposed. This is wrong, only the creator of an object should dispose of it. 