Change the captcha keyboard to textVisiblePassword

This is an advantage, because it replaces the autocorrect area with
numbers (which is useful for number only captchas)

Shamelessly stealing idea from thread

Clover/app/src/main/res/layout/layout_captcha_legacy.xml

@@ -37,7 +37,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
             android:layout_height="match_parent"
             android:layout_weight="1"
             android:hint="@string/reply_captcha_text"
-            android:inputType="textFilter"
+            android:inputType="textVisiblePassword"
             android:singleLine="true"
             android:textSize="16sp" />