Refactor base64 decode function to simplify handling (#3411)

Refactored the decode function to simplify base64 decoding and improve handling of various base64 formats. Removed redundant code and improved clarity.

V2rayNG/app/src/main/kotlin/com/v2ray/ang/util/Utils.kt

@@ -97,14 +97,10 @@ object Utils {
      * base64 decode
      */
     fun decode(text: String?): String {
-        tryDecodeBase64(text)?.let { return it }
-        if (text?.endsWith('=')==true) {
-            // try again for some loosely formatted base64
-            tryDecodeBase64(text.trimEnd('='))?.let { return it }
-        }
-        return ""
+        return tryDecodeBase64(text) ?: text?.trimEnd('=')?.let { tryDecodeBase64(it) } ?: ""
     }
 
+
     fun tryDecodeBase64(text: String?): String? {
         try {
             return Base64.decode(text, Base64.NO_WRAP).toString(Charsets.UTF_8)