gpui: Pre-allocate paths in open file dialog (#32106)

Pre-allocates the required memory for storing paths returned by open
file dialog on windows

Release Notes:

- N/A

crates/gpui/src/platform/windows/platform.rs

@@ -780,7 +780,7 @@ fn file_open_dialog(options: PathPromptOptions) -> Result<Option<Vec<PathBuf>>>
         return Ok(None);
     }
 
-    let mut paths = Vec::new();
+    let mut paths = Vec::with_capacity(file_count as usize);
     for i in 0..file_count {
         let item = unsafe { results.GetItemAt(i)? };
         let path = unsafe { item.GetDisplayName(SIGDN_FILESYSPATH)?.to_string()? };