Bump gfx-backend-metal from 0.9.0 to 0.9.1

Bumps [gfx-backend-metal](https://github.com/gfx-rs/gfx) from 0.9.0 to 0.9.1.
- [Release notes](https://github.com/gfx-rs/gfx/releases)
- [Changelog](https://github.com/gfx-rs/gfx/blob/master/CHANGELOG.md)
- [Commits](https://github.com/gfx-rs/gfx/commits)

---
updated-dependencies:
- dependency-name: gfx-backend-metal
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

Diff for: Cargo.lock

@@ -21,7 +21,7 @@ gfx-backend-empty = "=0.9.0"
 
 # GFX-RS backends
 gfx-backend-gl = { version="=0.9.0", optional = true }
-gfx-backend-metal = { version="=0.9.0", optional = true }
+gfx-backend-metal = { version="=0.9.1", optional = true }
 gfx-backend-vulkan = { version="=0.9.0", optional = true }
 gfx-backend-dx11 = { version="=0.9.0", optional = true }
 gfx-backend-dx12 = { version="=0.9.0", optional = true }