Use our own translation for "OK"

I missed this in the PR that it came with, but I guess it'll be useful if we go multiplatform.

app/src/main/java/eu/kanade/tachiyomi/ui/main/MainActivity.kt

@@ -254,7 +254,7 @@ class MainActivity : BaseActivity() {
                     },
                     confirmButton = {
                         TextButton(onClick = { showChangelog = false }) {
-                            Text(text = stringResource(android.R.string.ok))
+                            Text(text = stringResource(R.string.action_ok))
                         }
                     },
                 )

app/src/main/java/eu/kanade/tachiyomi/ui/reader/ReaderPageDialog.kt

@@ -89,7 +89,7 @@ private fun SetCoverDialog(
         },
         confirmButton = {
             TextButton(onClick = onConfirm) {
-                Text(stringResource(android.R.string.ok))
+                Text(stringResource(R.string.action_ok))
             }
         },
         dismissButton = {