message: doc: update readme on how to reset workspace override toolchain.
diff: @@ -212,7 +212,7 @@ The format below is: "`lean4.commandName` (command name): description", where `l
  Lean 4 file, the language server needs to be manually informed that it should re-elaborate the full file, including the
  imports. This command has a default keyboard binding of <kbd>Ctrl</kbd>+<kbd>Shift</kbd>+<kbd>X</kbd>.
  -* `lean4.selectToolchain` (Lean 4: Select Lean Toolchain) Select version of the Lean toolchain to use for the current workspace. This shows the list of available toolchains returned from `elan toolchain list` and allows you to easily switch. The Lean 4 language server will automatically be restarted using the selected toolchain. This command also provides a choice labelled `Other...` where you can enter the full path to a Lean 4 executable to use instead. This choice is remembered in your [Workspace Settings](https://code.visualstudio.com/docs/getstarted/settings) and you can reset any custom path by setting `Custom` back to the string `lean`.
  +* `lean4.selectToolchain` (Lean 4: Select Lean Toolchain) Select version of the Lean toolchain to use for the current workspace. This shows the list of available toolchains returned from `elan toolchain list` and allows you to easily switch. The Lean 4 language server will automatically be restarted using the selected toolchain. This command also provides a choice labelled `Other...` where you can enter the full path to a Lean 4 executable to use instead. This choice is remembered in your [Workspace Settings](https://code.visualstudio.com/docs/getstarted/settings) and you can reset any custom choice by selecting `Reset workspace override...` from the list (if it is shown).
  ![select-toolchain](vscode-lean4/media/select-toolchain.png)
  