For #8017: remove redundant string per localization team (#9068)

Based on conversation in https://github.com/mozilla-mobile/fenix/pull/8953#issuecomment-594332067

app/src/main/res/values/strings.xml

@@ -602,10 +602,8 @@
     <string name="preference_option_autoplay_allowed">Video and audio allowed</string>
     <!-- Label that indicates that all video and audio autoplay is allowed -->
     <string name="preference_option_autoplay_allowed2">Allow audio and video</string>
-    <!-- DEPRECATED: Label that indicates that video and audio autoplay is only allowed over WIFI -->
-    <string name="preference_option_autoplay_allowed_wifi_only">Allow audio and video on WIFI only</string>
     <!-- Label that indicates that video and audio autoplay is only allowed over WIFI -->
-    <string name="preference_option_autoplay_allowed_wifi_only2">Allow audio and video on Wi-Fi only</string>
+    <string name="preference_option_autoplay_allowed_wifi_only">Allow audio and video on Wi-Fi only</string>
     <!-- Label that indicates that video autoplay is allowed, but audio autoplay is blocked -->
     <string name="preference_option_autoplay_block_audio">Block audio</string>
     <!-- Label that indicates that all video and audio autoplay is blocked -->