enum fix for ktx/basis

[CedricGuillemet]

while investigating

https://forum.babylonjs.com/t/ktx2-ios-mipmap-issue/59136

Found an issue here:

Babylon.js/packages/tools/ktx2Decoder/src/Transcoders/mscTranscoder.ts

Line 146 in 2a36f70

const targetFormat = basisModule.TranscodeTarget[KTX2.TranscodeTarget[dst]]; // works because the labels of the sourceTextureFormat enum are the same as the property names used in TranscodeTarget!

To make it short, KTX2.TranscodeTarget[dst] returned ASTC_4X4_RGBA while expected value for basis is ASTC_4x4_RGBA. Keeping old enum value to not break back compat.

[bjsplat]

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[sebavan]

This is so sneaky... it took me ages to get it :-)