Happy Ghast Spawn Eggs do not have a small chance of summoning a Ghastling

Unlike other spawn eggs for mobs that have a baby variant, using a Happy Ghast Spawn Egg does not have a small chance of summoning a Ghastling instead of an adult Happy Ghast. This is also out of parity with Bedrock Edition, in which Happy Ghast Spawn Eggs have a 5% chance of summoning a Ghastling instead

To replicate:

1. Go into Creative Mode

2. Grab a Happy Ghast Spawn Egg

3. Summon many Happy Ghasts (be sure not to summon them on top of an existing Happy Ghast, which will always produce a Ghastling. This bug specifically refers to how summoning a Happy Ghast on its own never randomly summons a Ghastling)

4. Notice how a Ghastling is never summoned