fix(release): Unable to start activity: MultimediaActivity

We got the following truncated stack trace due to proguard/minify

```
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.ichi2.anki/com.ichi2.anki.multimedia.MultimediaActivity}: android.os.BadParcelableException: Parcelable encountered IOException reading a Serializable object (name = com.ichi2.anki.multimedia.f)
	at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:4377)
	at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:4574)
	...
	at android.os.Looper.loop(Looper.java:393)
	at android.app.ActivityThread.main(ActivityThread.java:9549)
	at java.lang.reflect.Method.invoke(Native Method)
	at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:600)
	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1005)
Caused by: android.os.BadParcelableException: Parcelable encountered IOException reading a Serializable object (name = com.ichi2.anki.multimedia.f)
	at android.os.Parcel.readSerializableInternal(Parcel.java:5410)
	at android.os.Parcel.readValue(Parcel.java:4928)
	at android.os.Parcel.readValue(Parcel.java:4625)
	...
	at android.os.Bundle.getSerializable(Bundle.java:1283)
	at com.ichi2.compat.CompatV33.getSerializable(CompatV33.kt:47)
	at com.ichi2.compat.CompatHelper$Companion.getSerializableCompat(CompatHelper.java:85)
	at com.ichi2.anki.multimedia.MultimediaActivity.getMultimediaArgsExtra(MultimediaActivity.kt:66)
	at com.ichi2.anki.multimedia.MultimediaActivity.onCreate(MultimediaActivity.kt:96)
	at android.app.Activity.performCreate(Activity.java:9196)
Caused by: java.io.InvalidClassException: m4.d; no valid constructor
	at java.io.ObjectStreamClass$ExceptionInfo.newInvalidClassException(ObjectStreamClass.java:163)
	at java.io.ObjectStreamClass.checkDeserialize(ObjectStreamClass.java:832)
```

I was unable to reproduce this issue locally, and it's easier to ignore
a few classes, since we're close to a public release and this is a blocker

Hopefully fixes 18712

(cherry picked from commit b73ac85)

Author: david-allison

AnkiDroid/proguard-rules.pro

@@ -25,6 +25,9 @@
 
 # Used through Reflection
 -keep class com.ichi2.anki.**.*Fragment { *; }
+# 18712: MultimediaActivity: android.os.BadParcelableException
+# TODO: this is brittle; IMultimediaEditableNote should implement Parcelable
+-keep class com.ichi2.anki.**.multimediacard.** { *; }
 -keep class * extends com.google.protobuf.GeneratedMessageLite { *; }
 -keep class androidx.core.app.ActivityCompat$* { *; }
 -keep class androidx.concurrent.futures.** { *; }