[Release] update library version to 1.6.0-alpha01

PiperOrigin-RevId: 412936540

build.gradle

@@ -59,7 +59,7 @@ ext {
     ? project.property('mavenRepoUrl') : '/tmp/myRepo/')
 
   // Current version of the library (could be in-development/unreleased).
-  mdcLibraryVersion = '1.5.0-alpha05'
+  mdcLibraryVersion = '1.6.0-alpha01'
   mdcLibraryPackage = "com.google.android.material"
   mdcLibraryDir = "com/google/android/material"
 }