refactor: delete 'c-' class prefix, update coreui styles to alpha-v13

src/views/icons/Flags.vue

@@ -5,8 +5,8 @@
         <i class="cui-globe"></i> Flags
       </CCardHeader>
       <CCardBody>
-        <CRow class="c-text-center">
-          <CCol class="c-mb-5" col="12">
+        <CRow class="text-center">
+          <CCol class="mb-5" col="12">
             <!-- For using the flags inline with text add the classes
             <code>.flag-icon</code> and <code>.flag-icon-xx</code>
             (where xx is the ISO 3166-1-alpha-2 code of a country) to an empty
@@ -15,7 +15,7 @@
           </CCol>
           <template v-for="(flag, key) in displayedFlags">
             <CCol
-              class="c-mb-5"
+              class="mb-5"
               col="3"
               sm="2"
               :key="key"