Update CITATION files for 9.4.0 release

Author: kbevers

CITATION

@@ -1,6 +1,6 @@
 To cite PROJ in publications use:
 
-  PROJ contributors (2023). PROJ coordinate transformation software
+  PROJ contributors (2024). PROJ coordinate transformation software
   library. Open Source Geospatial Foundation. URL https://proj.org/.
   DOI: 10.5281/zenodo.5884394
 
@@ -12,7 +12,7 @@ A BibTeX entry for LaTeX users is
     title = {{PROJ} coordinate transformation software library},
     author = {{PROJ contributors}},
     organization = {Open Source Geospatial Foundation},
-    year = {2023},
+    year = {2024},
     url = {https://proj.org/},
     doi = {10.5281/zenodo.5884394},
   }

CITATION.cff

@@ -2,8 +2,8 @@ cff-version: 1.2.0
 message: Please cite this software using these metadata or in the CITATION file.
 type: software
 title: PROJ
-version: 9.3.0
-date-released: 2023-09-01
+version: 9.4.0
+date-released: 2024-03-01
 doi: 10.5281/zenodo.5884394
 abstract: PROJ is a generic coordinate transformation software that transforms
   geospatial coordinates from one coordinate reference system (CRS) to another.