fix invalid documentation warning in price.move

[juzybits]

Summary

Adds a missing / to a documentation comment.

Rationale

Sui projects that depend on Pyth are getting a lengthy warning every time they sui move build or sui move test:

How has this been tested?

• Current tests cover my changes
• I changed my Pyth dependency in Move.toml from git to local to confirm that the warning is gone.

[vercel]

@juzybits is attempting to deploy a commit to the Pyth Network Team on Vercel.

A member of the Team first needs to authorize it.