Remove unused default feature from bevy_window

[BD103]

Objective

• Extracted from Fix bevy_window failing with serialize feature #14298.
• bevy_window has an empty default feature that does not enable anything, which is equivalent to not having any default features.

Solution

• Remove it :)
  • This is technically a breaking change, but specifying features = ["default"] manually in Cargo.toml is highly discouraged, so the impact is low.

---

Migration Guide

bevy_window had an empty default feature flag that did not do anything, so it was removed. You may have to remove any references to it if you specified it manually.

# 0.14
[dependencies]
bevy_window = { version = "0.14", default-features = false, features = ["default"] }

# 0.15
[dependencies]
bevy_window = { version = "0.15", default-features = false }

[alice-i-cecile]

@BD103 this will need to have merge conflicts resolved in a bit :) Ping me when it's ready again.

[BD103]

@alice-i-cecile done!