gpui: Make image example work regardless of how it is run (#24645)

This PR updates the GPUI `image` example such that it works when run in
the following ways:

- `cargo run -p gpui --example image` from the repository root
- `cargo run --example image` from within `crates/gpui`

Release Notes:

- N/A

crates/gpui/Cargo.toml

@@ -202,11 +202,12 @@ windows-core = "0.58"
 backtrace = "0.3"
 collections = { workspace = true, features = ["test-support"] }
 env_logger.workspace = true
-rand.workspace = true
-util = { workspace = true, features = ["test-support"] }
 http_client = { workspace = true, features = ["test-support"] }
-unicode-segmentation.workspace = true
 lyon = { version = "1.0", features = ["extra"] }
+rand.workspace = true
+unicode-segmentation.workspace = true
+reqwest_client = { workspace = true, features = ["test-support"] }
+util = { workspace = true, features = ["test-support"] }
 
 [target.'cfg(target_os = "windows")'.build-dependencies]
 embed-resource = "3.0"