This version of Unity is unsupported.
Method group is Obsolete

TextureFormat.ASTC_RGBA_6x6

Obsolete Enum member TextureFormat.ASTC_RGBA_6x6 has been deprecated. Use ASTC_6x6 instead.
Upgrade to ASTC_6x6

Description

ASTC (6x6 pixel block in 128 bits) compressed RGBA texture format.

See Also: TextureImporter.textureFormat.