build: disable must-use-promises check in ts_library tsetse for tests as... (#31325)

...tsetse now falsely asserting on  some lines in a few tests such as packages/core/schematics/test/injectable_pipe_migration_spec.ts.

```
    await runMigration();
    expect(tree.readContent('/index.ts'))
```

it asserts that "await is required on promise" on the 2nd line when there is no promise there

PR Close #31325

packages/tsconfig-test.json

@@ -5,6 +5,10 @@
   "extends": "./tsconfig-build.json",
   "compilerOptions": {
     "types": ["node", "jasmine"],
+    "plugins": [{
+        "name": "@bazel/tsetse",
+        "disabledRules": ["must-use-promises"],
+    }],
   },
   "bazelOptions": {
     "suppressTsconfigOverrideWarnings": true,