clang-tidy: fix warning on unused member

Resolve the following:

```
../src/version.hpp:146:23: error: private field 'bus' is not used [-Werror,-Wunused-private-field]
  146 |     sdbusplus::bus_t& bus;
```

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: Ifadd63dfbd7a0903b6f3cd5a7cb060be51006e5f
diff --git a/src/version.hpp b/src/version.hpp
index ed016e2..4722d93 100644
--- a/src/version.hpp
+++ b/src/version.hpp
@@ -77,7 +77,7 @@
             VersionPurpose versionPurpose, eraseFunc callback) :
         VersionInherit(bus, (objPath).c_str(),
                        VersionInherit::action::defer_emit),
-        eraseCallback(std::move(callback)), bus(bus), objPath(objPath),
+        eraseCallback(std::move(callback)), objPath(objPath),
         versionId(versionId), versionStr(versionString)
     {
         // Set properties.
@@ -142,9 +142,6 @@
     }
 
   private:
-    /** @brief Persistent sdbusplus DBus bus connection */
-    sdbusplus::bus_t& bus;
-
     /** @brief Persistent DBus object path */
     std::string objPath;