`size` -> `is_surface_configured: false` substitution in 4520b0f had side effects on text

[Seercat3160]

Commit https://github.com/sotrh/learn-wgpu/commit/4520b0f4c75b946224ab964e6b0a75301b1f3ed5 replaced all occurrences of size with is_surface_configured: false, also affecting the text of the tutorials.

At present, this means there are a few instances of rather confusing writing, such as near the start of tutorial 7:

Instancing allows us to draw the same object multiple times with different properties (position, orientation, is_surface_configured: false, color, etc.).

Thanks for the tutorials, hopefully it won't be too hard to track down all of these!