Update Registry references

[chrisn]

The EME spec refers to a Stream Format and Initialization Data Format Registry, in two places:

Section 8.9.2 Interoperably Encrypted

Note: The Encrypted Media Extensions Stream Format and Initialization Data Format Registry [EME-STREAM-REGISTRY] provides references to such stream formats.

Section 2 Definitions (Initialization Data)

The Encrypted Media Extensions Stream Format and Initialization Data Format Registry [EME-INITDATA-REGISTRY] provides the mapping from Initialization Data Type string to the specification for each format.

Today we have two distinct (but interrelated) registries:

• Encrypted Media Extensions Initialization Data Format Registry
• Encrypted Media Extensions Stream Format Registry

Were these a single registry at some point in history, then separated, but the spec not updated?

In any case, the text in the EME spec needs updating.