kokoro/presubmit: Add a dot argument to find
kokoro/presubmit: Add a dot argument to find

Without it, on my mac I get:

```
Running check clang-format... find: illegal option -- n
usage: find [-H | -L | -P] [-EXdsx] [-f path] path ... [expression]
       find [-H | -L | -P] [-EXdsx] -f path [path ...] [expression]
```

google/agi,pmuetschard/gapid,google/gapid,pmuetschard/gapid,google/gapid,pmuetschard/gapid,pmuetschard/gapid,google/gapid,Qining/gapid,google/agi,pmuetschard/gapid,google/gapid,google/agi,google/gapid,google/gapid,google/agi,google/agi,Qining/gapid,Qining/gapid,pmuetschard/gapid,google/gapid,Qining/gapid,pmuetschard/gapid,google/agi,Qining/gapid,google/agi,Qining/gapid,Qining/gapid,google/agi,pmuetschard/gapid,google/gapid,Qining/gapid