Update LICENSE.txt

Correctly name the 3-clause BSD license

(4th clause has never been part of it and the redundant 4rd point (same as 3) has been removed)

Author: (Py)thon (Co)llective (M)acro-(P)article Simulation (L)ibrary with (E)xtendible (T)racking (E)lements

LICENSE.txt

@@ -1,8 +1,12 @@
-BSD 4-Clause License
+BSD 3-Clause License
 
 Copyright (c) 2018, CERN
 All rights reserved.
 
+In applying this licence, CERN does not waive the privileges and immunities
+granted to it by virtue of its status as an Intergovernmental Organization
+or submit itself to any jurisdiction.
+
 Redistribution and use in source and binary forms, with or without
 modification, are permitted provided that the following conditions are met:
 
@@ -17,10 +21,6 @@ modification, are permitted provided that the following conditions are met:
   contributors may be used to endorse or promote products derived from
   this software without specific prior written permission.
 
-* Neither the name of the copyright holder nor the names of its contributors
-  may be used to endorse or promote products derived from this software
-  without specific prior written permission.
-
 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
@@ -31,6 +31,3 @@ SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-
-In applying this licence, CERN does not waive the privileges and immunities granted to it by virtue of its
-status as an Intergovernmental Organization or submit itself to any jurisdiction.