Update existing 3PID management UX

This tweaks the appearance of the existing 3PID management UX to use a different
style for the remove button. This styling will more closely match the soon to be
added 3PID discovery settings.

Part of https://github.com/vector-im/riot-web/issues/10159

res/css/views/settings/_EmailAddresses.scss

@@ -15,6 +15,8 @@ limitations under the License.
 */
 
 .mx_ExistingEmailAddress {
+    display: flex;
+    align-items: center;
     margin-bottom: 5px;
 }
 
@@ -24,14 +26,12 @@ limitations under the License.
     vertical-align: middle;
 }
 
-.mx_ExistingEmailAddress_email {
-    vertical-align: middle;
-}
-
+.mx_ExistingEmailAddress_email,
 .mx_ExistingEmailAddress_promptText {
+    flex: 1;
     margin-right: 10px;
 }
 
 .mx_ExistingEmailAddress_confirmBtn {
-    margin-right: 5px;
+    margin-left: 5px;
 }

res/css/views/settings/_PhoneNumbers.scss

@@ -15,6 +15,8 @@ limitations under the License.
 */
 
 .mx_ExistingPhoneNumber {
+    display: flex;
+    align-items: center;
     margin-bottom: 5px;
 }
 
@@ -24,16 +26,14 @@ limitations under the License.
     vertical-align: middle;
 }
 
-.mx_ExistingPhoneNumber_address {
-    vertical-align: middle;
-}
-
+.mx_ExistingPhoneNumber_address,
 .mx_ExistingPhoneNumber_promptText {
+    flex: 1;
     margin-right: 10px;
 }
 
 .mx_ExistingPhoneNumber_confirmBtn {
-    margin-right: 5px;
+    margin-left: 5px;
 }
 
 .mx_PhoneNumbers_input {