Fix spurious regex simpliciation

Android Studio claims this escaping isn't required, but now it's removed this code crashes due to a malformed regex.

PiperOrigin-RevId: 279501823

library/core/src/main/java/com/google/android/exoplayer2/text/ssa/SsaDecoder.java

@@ -198,7 +198,7 @@ public final class SsaDecoder extends SimpleSubtitleDecoder {
 
     String text =
         lineValues[formatTextIndex]
-            .replaceAll("\\{.*?}", "")
+            .replaceAll("\\{.*?\\}", "") // Warning that \\} can be replaced with } is bogus.
             .replaceAll("\\\\N", "\n")
             .replaceAll("\\\\n", "\n");
     cues.add(new Cue(text));