chore: simplify css pruning slightly (#14432)

packages/svelte/src/compiler/phases/2-analyze/css/css-prune.js

@@ -944,15 +944,16 @@ function get_possible_element_siblings(node, adjacent_only) {
 	let prev = node;
 	while ((prev = find_previous_sibling(prev))) {
 		if (prev.type === 'RegularElement') {
-			if (
-				!prev.attributes.find(
+			const has_slot_attribute = prev.attributes.some(
 				(attr) => attr.type === 'Attribute' && attr.name.toLowerCase() === 'slot'
-				)
-			) {
+			);
+
+			if (!has_slot_attribute) {
 				result.set(prev, NODE_DEFINITELY_EXISTS);
-			}
+
 				if (adjacent_only) {
-				break;
+					return result;
+				}
 			}
 		} else if (is_block(prev)) {
 			const possible_last_child = get_possible_last_child(prev, adjacent_only);
@@ -971,7 +972,6 @@ function get_possible_element_siblings(node, adjacent_only) {
 		}
 	}
 
-	if (!prev || !adjacent_only) {
 	/** @type {Compiler.SvelteNode | null} */
 	let parent = node;
 
@@ -993,7 +993,6 @@ function get_possible_element_siblings(node, adjacent_only) {
 			break;
 		}
 	}
-	}
 
 	return result;
 }