sync_watch: remove unused 'loop' member

Clang-19 warns about an unused member, which is indeed unused, so
remove it.

```
../sync_watch.hpp:73:15: error: private field 'loop' is not used [-Werror,-Wunused-private-field]
   73 |     sd_event& loop;
```

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I3836822d8ebd4b9b1bb219be0583636ae8a47b96
diff --git a/sync_watch.cpp b/sync_watch.cpp
index f3bf636..32e75c4 100644
--- a/sync_watch.cpp
+++ b/sync_watch.cpp
@@ -36,7 +36,7 @@
 
 SyncWatch::SyncWatch(sd_event& loop,
                      std::function<int(int, fs::path&)> syncCallback) :
-    inotifyFd(-1), syncCallback(std::move(syncCallback)), loop(loop)
+    inotifyFd(-1), syncCallback(std::move(syncCallback))
 {
     auto fd = inotify_init1(IN_NONBLOCK);
     if (-1 == fd)
diff --git a/sync_watch.hpp b/sync_watch.hpp
index f91ce29..0980cdf 100644
--- a/sync_watch.hpp
+++ b/sync_watch.hpp
@@ -68,9 +68,6 @@
 
     /** @brief The callback function for processing the inotify event */
     std::function<int(int, fs::path&)> syncCallback;
-
-    /** @brief Persistent sd_event loop */
-    sd_event& loop;
 };
 
 } // namespace manager