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/language_tools/src/lsp_log_tests.rs

@@ -15,9 +15,7 @@ use util::path;
 
 #[gpui::test]
 async fn test_lsp_logs(cx: &mut TestAppContext) {
-    if std::env::var("RUST_LOG").is_ok() {
-        env_logger::init();
-    }
+    zlog::init_test();
 
     init_test(cx);