Don't run cache priming when disabled in settings

What a single operator precedence can do :)
diff --git a/crates/rust-analyzer/src/main_loop.rs b/crates/rust-analyzer/src/main_loop.rs
index 7b339fa..8b4748d 100644
--- a/crates/rust-analyzer/src/main_loop.rs
+++ b/crates/rust-analyzer/src/main_loop.rs
@@ -485,8 +485,8 @@
                 }
                 // delay initial cache priming until proc macros are loaded, or we will load up a bunch of garbage into salsa
                 let proc_macros_loaded = self.config.prefill_caches()
-                    && !self.config.expand_proc_macros()
-                    || self.fetch_proc_macros_queue.last_op_result().copied().unwrap_or(false);
+                    && (!self.config.expand_proc_macros()
+                        || self.fetch_proc_macros_queue.last_op_result().copied().unwrap_or(false));
                 if proc_macros_loaded {
                     self.prime_caches_queue.request_op("became quiescent".to_owned(), ());
                 }