Never run transactions using serializable isolation (#33780)

We believe this is causing the database to execute certain queries very
slowly, and it's unclear whether we're actually benefitting from it.

Release Notes:

- N/A

crates/collab/src/db/tests.rs

@@ -17,11 +17,15 @@ use crate::migrations::run_database_migrations;
 use super::*;
 use gpui::BackgroundExecutor;
 use parking_lot::Mutex;
+use rand::prelude::*;
 use sea_orm::ConnectionTrait;
 use sqlx::migrate::MigrateDatabase;
-use std::sync::{
-    Arc,
-    atomic::{AtomicI32, AtomicU32, Ordering::SeqCst},
+use std::{
+    sync::{
+        Arc,
+        atomic::{AtomicI32, AtomicU32, Ordering::SeqCst},
+    },
+    time::Duration,
 };
 
 pub struct TestDb {
@@ -41,9 +45,7 @@ impl TestDb {
         let mut db = runtime.block_on(async {
             let mut options = ConnectOptions::new(url);
             options.max_connections(5);
-            let mut db = Database::new(options, Executor::Deterministic(executor.clone()))
-                .await
-                .unwrap();
+            let mut db = Database::new(options).await.unwrap();
             let sql = include_str!(concat!(
                 env!("CARGO_MANIFEST_DIR"),
                 "/migrations.sqlite/20221109000000_test_schema.sql"
@@ -60,6 +62,7 @@ impl TestDb {
         });
 
         db.test_options = Some(DatabaseTestOptions {
+            executor,
             runtime,
             query_failure_probability: parking_lot::Mutex::new(0.0),
         });
@@ -93,9 +96,7 @@ impl TestDb {
             options
                 .max_connections(5)
                 .idle_timeout(Duration::from_secs(0));
-            let mut db = Database::new(options, Executor::Deterministic(executor.clone()))
-                .await
-                .unwrap();
+            let mut db = Database::new(options).await.unwrap();
             let migrations_path = concat!(env!("CARGO_MANIFEST_DIR"), "/migrations");
             run_database_migrations(db.options(), migrations_path)
                 .await
@@ -105,6 +106,7 @@ impl TestDb {
         });
 
         db.test_options = Some(DatabaseTestOptions {
+            executor,
             runtime,
             query_failure_probability: parking_lot::Mutex::new(0.0),
         });