fix: align select placeholder text color with other fields (#10131)

Author: jouni

packages/select/src/styles/vaadin-select-value-button-base-styles.js

@@ -24,6 +24,10 @@ export const valueButton = css`
     display: contents;
   }
 
+  :host([placeholder]) {
+    color: var(--vaadin-input-field-placeholder-color, var(--vaadin-color-subtle));
+  }
+
   :host([disabled]) {
     pointer-events: none;
   }