Updated citation and test files to new patch release 1.6.1.

Author: Johannes Markert

CITATION.cff

@@ -1,6 +1,6 @@
 title: t8code
-version: 1.6.0
-date-released: "2023-12-01"
+version: 1.6.1
+date-released: "2023-12-06"
 repository-code: "https://github.com/dlr-amr/t8code"
 url: "https://dlr-amr.github.io/t8code/"
 doi: "10.5281/zenodo.7034838"

test/t8_gtest_version.cxx

@@ -27,7 +27,7 @@
 /* The following three tests check whether t8code computes the correct
  * version.
  * The current version of t8code is
- *    1.6.0
+ *    1.6.1
  * If you increase the major or minor version number, you need to adjust these tests and
  * this comment. */