Fix oppia#3842: Remove second/millisecond conversion check for greeti…

…ng timestamp (oppia#5536)

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Fixes oppia#3842 

This PR removes the `ensureTimestampIsInMilliseconds` function from
`TextViewBindingAdapters`, eliminating the need for the
second-to-millisecond conversion check for greeting timestamps.

### Sreenshots
|Before|After|
|--|--|
|![WhatsApp Image 2024-09-17 at 11 36 52
AM](https://github.com/user-attachments/assets/0978ffe5-9457-4071-8828-a2791e7e4664)|![WhatsApp
Image 2024-09-17 at 11 39 41
AM](https://github.com/user-attachments/assets/5c41cdc1-5287-4979-8969-4057362434c9)|
## Essential Checklist
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app/src/main/java/org/oppia/android/app/databinding/TextViewBindingAdapters.java

@@ -68,15 +68,14 @@ public static void setDrawableEndCompat(
   }
 
   private static String getTimeAgo(View view, long lastVisitedTimestamp) {
-    long timeStampMillis = ensureTimestampIsInMilliseconds(lastVisitedTimestamp);
     long currentTimeMillis = getOppiaClock(view).getCurrentTimeMs();
     AppLanguageResourceHandler resourceHandler = getResourceHandler(view);
 
-    if (timeStampMillis > currentTimeMillis || timeStampMillis <= 0) {
+    if (lastVisitedTimestamp > currentTimeMillis || lastVisitedTimestamp <= 0) {
       return resourceHandler.getStringInLocale(R.string.last_logged_in_recently);
     }
 
-    long timeDifferenceMillis = currentTimeMillis - timeStampMillis;
+    long timeDifferenceMillis = currentTimeMillis - lastVisitedTimestamp;
 
     if (timeDifferenceMillis < (int) TimeUnit.MINUTES.toMillis(1)) {
       return resourceHandler.getStringInLocale(R.string.just_now);
@@ -112,15 +111,6 @@ private static String getPluralString(
         );
   }
 
-  private static long ensureTimestampIsInMilliseconds(long lastVisitedTimestamp) {
-    // TODO(#3842): Investigate & remove this check.
-    if (lastVisitedTimestamp < 1000000000000L) {
-      // If timestamp is given in seconds, convert that to milliseconds.
-      return TimeUnit.SECONDS.toMillis(lastVisitedTimestamp);
-    }
-    return lastVisitedTimestamp;
-  }
-
   private static AppLanguageResourceHandler getResourceHandler(View view) {
     AppLanguageActivityInjectorProvider provider =
         (AppLanguageActivityInjectorProvider) getAttachedActivity(view);