sensors: Align source structure away from anti-patterns

The anti-patterns document comments on source structure, specifically
on placing internal headers in a parallel subtree[1]. dbus-sensors is an
example of violating this anti-pattern, so fix it.

[1]: https://github.com/openbmc/docs/blob/master/anti-patterns.md#placing-internal-headers-in-a-parallel-subtree

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Change-Id: I50ecaddd53fa9c9b7a0441af9de5e60bd94e47c6
diff --git a/src/Thresholds.cpp b/src/Thresholds.cpp
index ee0456d..aa73063 100644
--- a/src/Thresholds.cpp
+++ b/src/Thresholds.cpp
@@ -1,8 +1,10 @@
-#include <Thresholds.hpp>
-#include <VariantVisitors.hpp>
+#include "Thresholds.hpp"
+
+#include "VariantVisitors.hpp"
+#include "sensor.hpp"
+
 #include <boost/algorithm/string/replace.hpp>
 #include <boost/container/flat_map.hpp>
-#include <sensor.hpp>
 
 #include <array>
 #include <cmath>