zlog: Replace usages of env_logger in tests with zlog (#31436)

Also fixes:
https://github.com/zed-industries/zed/pull/31400#issuecomment-2908165249

Release Notes:

- N/A *or* Added/Fixed/Improved ...

crates/remote_server/Cargo.toml

@@ -86,6 +86,7 @@ language_model = { workspace = true, features = ["test-support"] }
 lsp = { workspace = true, features=["test-support"] }
 unindent.workspace = true
 serde_json.workspace = true
+zlog.workspace = true
 
 [build-dependencies]
 cargo_toml.workspace = true