Upgrade fluent to minimize dependencies

[nelson137]

Upgrade fluent once they release a new version with this change to upgrade self_cell. This will reduce the double dependency:

warning[duplicate]: found 2 duplicate entries for crate 'self_cell'
    ┌─ /Users/nelson/Projects/Forks/bones/Cargo.lock:417:1
    │
417 │ ╭ self_cell 0.10.3 registry+https://github.com/rust-lang/crates.io-index
418 │ │ self_cell 1.0.3 registry+https://github.com/rust-lang/crates.io-index
    │ ╰─────────────────────────────────────────────────────────────────────^ lock entries
    │
    = self_cell v0.10.3
      └── fluent-bundle v0.15.2
          └── fluent v0.15.0
              └── bones_framework v0.3.0
                  ├── bones_bevy_renderer v0.3.0
                  │   ├── demo_assets_minimal v0.3.0
                  │   ├── demo_features v0.3.0
                  │   ├── demo_hello_world v0.3.0
                  │   └── demo_scripting v0.3.0
                  ├── demo_assets_minimal v0.3.0 (*)
                  ├── demo_features v0.3.0 (*)
                  ├── demo_hello_world v0.3.0 (*)
                  └── demo_scripting v0.3.0 (*)
    = self_cell v1.0.3
      └── self_cell v0.10.3
          └── fluent-bundle v0.15.2
              └── fluent v0.15.0
                  └── bones_framework v0.3.0
                      ├── bones_bevy_renderer v0.3.0
                      │   ├── demo_assets_minimal v0.3.0
                      │   ├── demo_features v0.3.0
                      │   ├── demo_hello_world v0.3.0
                      │   └── demo_scripting v0.3.0
                      ├── demo_assets_minimal v0.3.0 (*)
                      ├── demo_features v0.3.0 (*)
                      ├── demo_hello_world v0.3.0 (*)
                      └── demo_scripting v0.3.0 (*)

[alerque]

This change has been merged (via a different PR than you have linked, but the same change) and is not in Git master if you want to depend on that. It should be in the next fluent-fallback release, whatever number that ends up being (not the safe harbor one v0.7.1 that went out today, whatever is next).