prepare for 7.4

Version.txt

@@ -1,3 +1,3 @@
 OR_TOOLS_MAJOR=7
-OR_TOOLS_MINOR=3
+OR_TOOLS_MINOR=4
 #PRE_RELEASE=YES

tools/doc/gen_ref_doc.py

@@ -168,5 +168,5 @@ def create_section_data():
   return sections
 
 if __name__ == '__main__':
-  version_number = '7.3'
+  version_number = '7.4'
   main(version_number)

tools/generate_dotnet_proj.sh

@@ -11,7 +11,7 @@ declare -r SRC=$(basename "$FILE")
 # shellcheck disable=SC2155
 declare -r PACKAGES_PATH=$(realpath --relative-to="${FILE%/*}" packages)
 if [[ $FILE == *.cs ]] ; then
-  declare -r LANG_VERSION="    <LangVersion>7.3</LangVersion>"
+  declare -r LANG_VERSION="    <LangVersion>7.4</LangVersion>"
   declare -r OR_TOOLS_PKG="Google.OrTools"
 else
   declare -r LANG_VERSION=""