fix(button): fix iOS outline button color

fixes #4169

Author: nolimits4web

src/core/components/button/button-vars.less

@@ -41,7 +41,9 @@
   --f7-button-border-radius: 4px;
   --f7-button-font-weight: 600;
   --f7-button-letter-spacing: 0;
+  /*
   --f7-button-outline-border-color: var(--f7-theme-color);
+  */
   --f7-button-outline-border-width: 2px;
   /*
   --f7-button-pressed-bg-color: rgba(var(--f7-theme-color-rgb), .15);