[fenix] Revert "For 11660: fixing nits for previous https://github.com/mozilla-mobile/fenix/pull/11668 (https://github.com/mozilla-mobile/fenix/pull/11821)"

This reverts commit 220e98e4c2c45b12e982bc5d4082739812193629.

app/src/main/java/org/mozilla/fenix/FenixApplication.kt

@@ -257,9 +257,8 @@ open class FenixApplication : LocaleAwareApplication(), Provider {
         // no-op, LeakCanary is disabled by default
     }
 
-    /**
-     * See [TopsiteStore.prefetch] for details on pre fetching.
-     */
+    // This is for issue https://github.com/mozilla-mobile/fenix/issues/11660. We prefetch our info for startup
+    // so that we're sure that we have all the data available as our fragment is launched.
     private fun prefetchForHomeFragment() {
         StrictMode.allowThreadDiskReads().resetPoliciesAfter {
             components.core.topSiteStorage.prefetch()

app/src/main/java/org/mozilla/fenix/components/TopSiteStorage.kt

@@ -14,7 +14,7 @@ import mozilla.components.feature.top.sites.TopSite
 import mozilla.components.feature.top.sites.TopSiteStorage
 import mozilla.components.support.locale.LocaleManager
 import org.mozilla.fenix.R
-import org.mozilla.fenix.ext.observeOnceAndRemoveObserver
+import org.mozilla.fenix.ext.observeOnce
 import org.mozilla.fenix.ext.settings
 import org.mozilla.fenix.settings.SupportUtils
 import org.mozilla.fenix.settings.advanced.getSelectedLocale
@@ -88,15 +88,8 @@ class TopSiteStorage(private val context: Context) {
         }
     }
 
-    /**
-     * This is for issue https://github.com/mozilla-mobile/fenix/issues/11660. We prefetch the top
-     * sites for startup so that we're sure that we have all the data available as our fragment is
-     * launched to make sure that we can display everything on the home screen on the first drawing pass.
-     * This method doesn't negatively affect performance since the [getTopSites] runs on the a
-     * background thread.
-     */
     fun prefetch() {
-        getTopSites().observeOnceAndRemoveObserver {
+        getTopSites().observeOnce {
             cachedTopSites = it
         }
     }

app/src/main/java/org/mozilla/fenix/ext/LiveData.kt

@@ -10,11 +10,11 @@ import androidx.lifecycle.Observer
 /**
  * Observe a LiveData once and unregister from it as soon as the live data returns a value
  */
-fun <T> LiveData<T>.observeOnceAndRemoveObserver(callback: (T) -> Unit) {
+fun <T> LiveData<T>.observeOnce(observer: (T) -> Unit) {
     observeForever(object : Observer<T> {
         override fun onChanged(value: T) {
             removeObserver(this)
-            callback(value)
+            observer(value)
         }
     })
 }