Fix missing argument to --enable_display
`--enable_display` needs a value, and fails if passed just as-is.
Closes
@@ -329,7 +329,7 @@ graphical interface of the emulator while the test is running. To do this, pass
these test arguments to Bazel:
```
-bazel test //my/test:target --test_arg=--enable_display --test_env=DISPLAY
+bazel test //my/test:target --test_arg=--enable_display=true --test_env=DISPLAY
```
### Testing with a local emulator or device
