Add stefans comments from mattermost to signup page

Fixes:

Stefan Hugtenburg
11:36 AM

Zie net dat de tekst nog niet helemaal klopt 
Het is de Engelse test voor TA'ing (checkbox 1) en de TA-training (checkbox 2) (edited)

frontend/src/components/Credentials/Credentials.vue

@@ -23,7 +23,7 @@
 
         <div class="text-left">
           <b-form-checkbox v-model="en_test" class="text-left">
-            I have previously passed the English Test required for TA-training
+            I have previously passed the English Test required for TA'ing
             <b-btn size="sm" id="en_test_popover" variant="secondary">?</b-btn>
             <b-popover target="en_test_popover" placement="right" triggers="hover focus">
               Don't worry if you have not passed this yet. We will give you instructions about this if you are hired as a TA
@@ -31,7 +31,7 @@
           </b-form-checkbox>
           <br>
           <b-form-checkbox v-model="ta_test" class="text-left">
-            I passed my TA Test
+            I passed my TA-Training
           </b-form-checkbox>
           <br>
           <b-form-checkbox v-model="accept_gdpr" class="text-left">
@@ -63,4 +63,4 @@
 
 <script src='./Credentials.js'></script>
 
-<style scoped></style>
\ No newline at end of file
+<style scoped></style>