python: Properly check for Pyright language server in local environment (#24873)

Closes #24565 

As pointed out in
https://github.com/zed-industries/zed/issues/24565#issuecomment-2657822723
, the name for the Pyright language server is `pyright-langserver`, not
`pyright`. The latter is a CLI-tool as described in
https://microsoft.github.io/pyright/#/command-line which only provides
static type checking. It has neither LSP-capabilities nor a `--stdio`
argument. Thus, the error as shown in the linked issue appears.

I disagree with the fix as described in
https://github.com/zed-industries/zed/issues/24565#issuecomment-2657904208
, as it could only cause this error to reappear in rare scenarios where
Pyright, but not the Pyright language server is installed in a user's
environment. Just checking for `pyright-langserver` to be present in the
environment seems more straightforward here.

Release Notes:

- Python: Fixed Pyright failing to start when installed locally

Co-authored-by: Beniamin Zagan <47153906+beniaminzagan@users.noreply.github.com>

crates/languages/src/python.rs

@@ -83,7 +83,7 @@ impl LspAdapter for PythonLspAdapter {
         _: Arc<dyn LanguageToolchainStore>,
         _: &AsyncApp,
     ) -> Option<LanguageServerBinary> {
-        if let Some(pyright_bin) = delegate.which(Self::SERVER_NAME.as_ref()).await {
+        if let Some(pyright_bin) = delegate.which("pyright-langserver".as_ref()).await {
             let env = delegate.shell_env().await;
             Some(LanguageServerBinary {
                 path: pyright_bin,