Rewrite label_details_support condition to be consistent with other parts of the codebase.

Author: jaboatman

src/tools/rust-analyzer/crates/rust-analyzer/src/lsp/capabilities.rs

@@ -210,10 +210,7 @@ impl ClientCapabilities {
                 .completion_item
                 .as_ref()?
                 .label_details_support
-                .as_ref()
-        })()
-        .copied()
-        .unwrap_or_default()
+        })() == Some(true)
     }
 
     fn completion_item(&self) -> Option<CompletionOptionsCompletionItem> {