For #4844: fix file prefix url shortening

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

@@ -40,17 +40,12 @@ fun String.toShortUrl(publicSuffixList: PublicSuffixList): String {
     if (
         inputString.isEmpty() ||
         !URLUtil.isValidUrl(inputString) ||
-        inputString == FILE_PREFIX ||
+        inputString.startsWith(FILE_PREFIX) ||
         uri.port !in -1..MAX_VALID_PORT
     ) {
         return inputString
     }
 
-    if (inputString.startsWith(FILE_PREFIX)) {
-        // Strip file prefix and return the remainder
-        return inputString.substring(FILE_PREFIX.length)
-    }
-
     if (uri.host?.isIpv4() == true ||
         uri.isIpv6() ||
         // If inputString is just a hostname and not a FQDN, use the entire hostname.

app/src/test/java/org/mozilla/fenix/ext/StringTest.kt

@@ -186,8 +186,8 @@ class StringTest {
     }
 
     @Test
-    fun `should return not the protocol for file`() {
-        "file:///foo/bar.txt" shortenedShouldBecome "/foo/bar.txt"
+    fun `file uri should return input`() {
+        "file:///foo/bar.txt" shortenedShouldBecome "file:///foo/bar.txt"
     }
 
     @Test