graphics: clean up PixelFormat docs

Make the docs more self-contained, not referring to stuff not
defined by the HIDL interfaces.

Mark JPEG, YCBCR_422_888, YCBCR_444_888, FLEX_RGB_888,
FLEX_RGBA_8888 as "MUST NOT USE".  These format are never supposed
to be seen by gralloc and do not belong to the HIDL interfaces.

Note, current.txt change (as opposed to addition) is only allowed
because this is an unreleased interface.

Bug: 32593292
Test: builds
Change-Id: Ia7607cc73dd2f58dfa27e71b0004b21c7ca6904d
diff --git a/current.txt b/current.txt
index 4ecee9a..2893748 100644
--- a/current.txt
+++ b/current.txt
@@ -98,7 +98,7 @@
 17971eb8a482893dadcfc16e0583f492d42a034ef95d9b0b709417af30838396 android.hardware.graphics.allocator@2.0::IAllocator
 60bf42a4898e4fb70dbd720b263aeafd7f35f5e1a5effeabb4d5d659878a5f18 android.hardware.graphics.bufferqueue@1.0::IGraphicBufferProducer
 b8a75617b9ec12bea641f3a73d4025a33e8b9a2f9169dd46094af56adf9249c5 android.hardware.graphics.bufferqueue@1.0::IProducerListener
-3e7aa6cbfca575299bc511f618373576def6e07c5bf082d2b2f638be0d0d347c android.hardware.graphics.common@1.0::types
+78f973cf47a45d9d842c95888324dfc44e24a6fa3e5a1d0f726dfe37a863b634 android.hardware.graphics.common@1.0::types
 b3aac6c3817f039964fcd62268274b3039e17bd7d0d5b40b4d1d1c7b19a1f866 android.hardware.graphics.composer@2.1::IComposer
 b19d00eb8a8b3b0034a0321f22e8f32162bf4c2aebbce6da22c025f56e459ea2 android.hardware.graphics.composer@2.1::IComposerCallback
 e992684e690dfe67a8cbeab5005bfa3fa9c2bf3d4b0b75657fb1f0c2d5dd2bae android.hardware.graphics.composer@2.1::IComposerClient