test: physical: Fix modernize-return-braced-init-list

```
../test/physical.cpp:41:12: error: avoid repeating the return type from the declaration; use a braced initializer list instead [modernize-return-braced-init-list,-warnings-as-errors]
    return fs::path(dir);
           ^
```

Change-Id: I80ca69e7dba3443f74cd16b756407ee2368923be
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
diff --git a/test/physical.cpp b/test/physical.cpp
index 2c2f6f1..a8226a3 100644
--- a/test/physical.cpp
+++ b/test/physical.cpp
@@ -38,7 +38,7 @@
         throw std::system_error(errno, std::system_category());
     }
 
-    return fs::path(dir);
+    return dir;
 }
 
 class MockLed : public phosphor::led::SysfsLed