Update release notes + bump version

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=205660355

constants.gradle

@@ -13,8 +13,8 @@
 // limitations under the License.
 project.ext {
     // ExoPlayer version and version code.
-    releaseVersion = '2.8.2'
-    releaseVersionCode = 2802
+    releaseVersion = '2.8.3'
+    releaseVersionCode = 2803
     // Important: ExoPlayer specifies a minSdkVersion of 14 because various
     // components provided by the library may be of use on older devices.
     // However, please note that the core media playback functionality provided

library/core/src/main/java/com/google/android/exoplayer2/ExoPlayerLibraryInfo.java

@@ -29,11 +29,11 @@ public final class ExoPlayerLibraryInfo {
 
   /** The version of the library expressed as a string, for example "1.2.3". */
   // Intentionally hardcoded. Do not derive from other constants (e.g. VERSION_INT) or vice versa.
-  public static final String VERSION = "2.8.2";
+  public static final String VERSION = "2.8.3";
 
   /** The version of the library expressed as {@code "ExoPlayerLib/" + VERSION}. */
   // Intentionally hardcoded. Do not derive from other constants (e.g. VERSION) or vice versa.
-  public static final String VERSION_SLASHY = "ExoPlayerLib/2.8.2";
+  public static final String VERSION_SLASHY = "ExoPlayerLib/2.8.3";
 
   /**
    * The version of the library expressed as an integer, for example 1002003.
@@ -43,7 +43,7 @@ public final class ExoPlayerLibraryInfo {
    * integer version 123045006 (123-045-006).
    */
   // Intentionally hardcoded. Do not derive from other constants (e.g. VERSION) or vice versa.
-  public static final int VERSION_INT = 2008002;
+  public static final int VERSION_INT = 2008003;
 
   /**
    * Whether the library was compiled with {@link com.google.android.exoplayer2.util.Assertions}