Replaces "fxb/#" with the Monorail syntax "fuchsia:#".
This updates https://swiftshader-review.googlesource.com/c/SwiftShader/+/44129.

Bug: None
Change-Id: I9dc0e617cdec2d1a8b980ee7aca2c718ce4021d6
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/46328
Kokoro-Result: kokoro <noreply+kokoro@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Tested-by: David Dorwin <ddorwin@google.com>