Update dynamic links Android build's compile SDK version

Missed updating a number to 28.  While not technically necessary, since the targetSdkVersion is 28, for consistency with the other libraries dynamic links should be updated as well.

PiperOrigin-RevId: 256039327

Author: a-maurice

dynamic_links/build.gradle

@@ -31,7 +31,7 @@ allprojects {
 apply plugin: 'com.android.library'
 
 android {
-  compileSdkVersion 26
+  compileSdkVersion 28
   buildToolsVersion '28.0.3'
 
   sourceSets {