dbuspassive: drop needless c_str

The sdbusplus match constructor already handles a std::string, so
drop the extra c_str call.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I2167d2a027e13d55b5590b8266e56cc108b23bfa
diff --git a/dbus/dbuspassive.cpp b/dbus/dbuspassive.cpp
index 6ca0b42..ac0d5cf 100644
--- a/dbus/dbuspassive.cpp
+++ b/dbus/dbuspassive.cpp
@@ -92,7 +92,7 @@
     const SensorProperties& settings, bool failed, const std::string& path,
     const std::shared_ptr<DbusPassiveRedundancy>& redundancy) :
     ReadInterface(),
-    _signal(bus, getMatch(path).c_str(), dbusHandleSignal, this), _id(id),
+    _signal(bus, getMatch(path), dbusHandleSignal, this), _id(id),
     _helper(std::move(helper)), _failed(failed), path(path),
     redundancy(redundancy)