Update year in solver.h

Change-Id: I49ffe5a24786aa32e7677785cc91ee914956f2e6

include/ceres/solver.h

diff --git a/include/ceres/solver.h b/include/ceres/solver.h
index 3b15318..2a1dd18 100644
--- a/include/ceres/solver.h
+++ b/include/ceres/solver.h
@@ -1,5 +1,5 @@
 // Ceres Solver - A fast non-linear least squares minimizer
-// Copyright 2019 Google Inc. All rights reserved.
+// Copyright 2022 Google Inc. All rights reserved.
 // http://ceres-solver.org/
 //
 // Redistribution and use in source and binary forms, with or without