Fix using return instead of exit in pipx install script

packages/pipx.sh

@@ -2,13 +2,13 @@
 
 command -v python3 > /dev/null || {
     echo "python3 executable not found, exiting"
-    return 1
+    exit 1
 }
 
 python3 -c "import sys; assert sys.version_info[0] >= 3 and sys.version_info[1] >= 7" || {
     echo python3 --version
     echo "python version too old, requires >=3.7"
-    return 1
+    exit 1
 }
 
 USERSITE=$(python3 -c "import site; print(site._get_path(site._getuserbase()))")