Select applicable positions for lsp_ext methods more leniently (#32272)

Closes https://github.com/zed-industries/zed/issues/27238

Release Notes:

- Fixed `editor::SwitchSourceHeader` and
`editor::ExpandMacroRecursively` not working with text selections

crates/editor/src/rust_analyzer_ext.rs

@@ -132,9 +132,6 @@ pub fn expand_macro_recursively(
     window: &mut Window,
     cx: &mut Context<Editor>,
 ) {
-    if editor.selections.count() == 0 {
-        return;
-    }
     let Some(project) = &editor.project else {
         return;
     };