Drop support for Android 5.x

It's 5-6 years old, and only accounts for 2% of users in the Firebase analytics.

app/src/main/java/eu/kanade/tachiyomi/widget/ElevationAppBarLayout.kt

@@ -3,7 +3,6 @@ package eu.kanade.tachiyomi.widget
 import android.animation.ObjectAnimator
 import android.animation.StateListAnimator
 import android.content.Context
-import android.os.Build
 import android.util.AttributeSet
 import com.google.android.material.R
 import com.google.android.material.appbar.AppBarLayout
@@ -20,12 +19,7 @@ class ElevationAppBarLayout @JvmOverloads constructor(
     }
 
     fun enableElevation(liftOnScroll: Boolean) {
-        if (Build.VERSION.SDK_INT == Build.VERSION_CODES.LOLLIPOP) {
-            // Delay to avoid crash
-            post { setElevation(liftOnScroll) }
-        } else {
-            setElevation(liftOnScroll)
-        }
+        setElevation(liftOnScroll)
     }
 
     private fun setElevation(liftOnScroll: Boolean) {