Enable zstd content encoding support (obsolete)

OBSOLETE: This policy is obsolete and doesn't work after Microsoft Edge 137. This policy controls whether Microsoft Edge supports Zstandard (zstd) content encoding. If this policy is enabled, Microsoft Edge advertises zstd in the Accept-Encoding request header and can decompress responses encoded with zstd. If this policy is disabled, Microsoft Edge doesn't advertise or support zstd content encoding. If this policy is not configured, the default behavior is to enable support for zstd content encoding. NOTE: This policy is obsolete starting with Microsoft Edge version 138 because Microsoft Edge now always supports zstd content encoding.