Remove unnecessary CSS class nesting

[MAILPOET-2792]

assets/css/src/components-plugin/_premium-page.scss

@@ -30,7 +30,14 @@
     }
   }
 
-  .mailpoet-premium-page-intro {
+  @include breakpoint-max-width(1100px) {
+    h2 {
+      font-size: 2em; // The text WooCommerce is too long and so on smaller displays it overflows. This helps.
+    }
+  }
+}
+
+.mailpoet-premium-page-intro {
   display: flex;
   flex-direction: row;
   margin-bottom: 3em;
@@ -60,16 +67,16 @@
       text-align: center;
     }
   }
-  }
+}
 
-  .mailpoet-premium-page-bullet-list {
+.mailpoet-premium-page-bullet-list {
   li:before {
     content: '·';
     padding-right: 5px;
   }
-  }
+}
 
-  .mailpoet-premium-page-text {
+.mailpoet-premium-page-text {
   padding-bottom: 4em;
   text-align: center;
 
@@ -84,14 +91,14 @@
   .mailpoet-premium-page-paragraph-before-heading + h1 {
     margin-top: 0;
   }
-  }
+}
 
-  .mailpoet-premium-page-text-narrow {
+.mailpoet-premium-page-text-narrow {
   margin: auto;
   max-width: 700px;
-  }
+}
 
-  .mailpoet-premium-page-features {
+.mailpoet-premium-page-features {
   display: flex;
   flex-direction: row;
   flex-wrap: wrap;
@@ -113,9 +120,9 @@
       text-align: left;
     }
   }
-  }
+}
 
-  .mailpoet-premium-page-options {
+.mailpoet-premium-page-options {
   display: flex;
   flex-direction: row;
   flex-wrap: wrap;
@@ -148,15 +155,8 @@
       padding-right: 5px;
     }
   }
-  }
-
-  .mailpoet-premium-page-options-divider {
-    flex-grow: 100;
-  }
-
-  @include breakpoint-max-width(1100px) {
-    h2 {
-      font-size: 2em; // The text WooCommerce is too long and so on smaller displays it overflows. This helps.
-    }
-  }
+}
+
+.mailpoet-premium-page-options-divider {
+  flex-grow: 100;
 }