fix(webapp): class rename subheading → subtitle-1

fix missing migrations to vuetify v2
https://v2.vuetifyjs.com/en/getting-started/upgrade-guide/#typography

www/webapp/src/views/AboutPage.vue

@@ -13,7 +13,7 @@
         <v-row align="center">
           <v-col class="col-md-6 col-12 py-8 triangle-fg">
             <h1 class="text-h4 font-weight-bold">About Us</h1>
-            <h3 class="subheading mt-2 py-8 font-weight-regular">
+            <div class="text-subtitle-1 mt-2 py-8 font-weight-regular">
               <p>
                 Our services are operated by deSEC e.V., a registered non-profit organization in Berlin, Germany.
               </p>
@@ -21,7 +21,7 @@
                 As a charity, all operations abide by our statutes which define guidelines of all operations.
                 For details regarding our statutes, please refer to the legally binding version (German) below.
               </p>
-            </h3>
+            </div>
           </v-col>
         </v-row>
       </v-container>

www/webapp/src/views/DonatePage.vue

@@ -3,12 +3,12 @@
     <v-row align="center">
       <v-col class="col-md-6 col-12 py-8">
         <h1 class="text-h4 font-weight-bold">Donate to Support our Mission</h1>
-        <h3 class="subheading mt-6 font-weight-regular">
+        <div class="text-subtitle-1 mt-6 font-weight-regular">
           <p>
             Like our community service? Your donation shows us we're on the right track.
             All donations are used in accordance with <router-link :to="{name: 'about'}">our statutes</router-link>.
           </p>
-        </h3>
+        </div>
       </v-col>
     </v-row>
     <v-row>

www/webapp/src/views/HomePage.vue

@@ -6,7 +6,7 @@
       <v-row align="center">
         <v-col class="col-md-6 col-12 py-8 triangle-fg">
           <h1 class="text-h4 font-weight-bold">Modern DNS Hosting for Everyone</h1>
-          <h3 class="subheading mt-2 pt-8 font-weight-regular">
+          <div class="text-subtitle-1 mt-2 pt-8 font-weight-regular">
             <p>
               deSEC is a <strong>free DNS hosting</strong> service, <strong>designed with security in mind</strong>.
             </p>
@@ -14,7 +14,7 @@
               Running on <strong>open-source software</strong> and <strong>supported by <a href="https://securesystems.de/">SSE</a></strong>,
               deSEC is free for everyone to use.
             </p>
-          </h3>
+          </div>
           <div class="pa-2" v-if="!user.authenticated">
             <v-form @submit.prevent="signup" :value="valid" ref="form">
               <v-row>

www/webapp/src/views/TermsPage.vue

@@ -6,7 +6,7 @@
       <v-row align="center">
         <v-col class="col-md-6 col-12 py-8 triangle-fg">
           <h1 class="text-h4 font-weight-bold">Terms of Use</h1>
-          <h3 class="subheading mt-2 py-8 font-weight-regular">
+          <div class="text-subtitle-1 mt-2 py-8 font-weight-regular">
             <p>
               We collect as little data as possible and restrict the usage of our DNS service only where necessary to
               meet legal requirements or to ensure the smooth operation of our services. In turn, we rely on the
@@ -16,7 +16,7 @@
               Our <router-link :to="{name: 'privacy-policy'}">Privacy Policy</router-link> is also part of the
               agreement between deSEC and its users.
             </p>
-          </h3>
+          </div>
         </v-col>
       </v-row>
     </v-container>