Update cheatsheets

tldr/unset

@@ -0,0 +1,21 @@
+---
+syntax: markdown
+tags: [tldr, common]
+source: https://github.com/tldr-pages/tldr.git
+---
+# unset
+
+> Remove shell variables or functions.
+> More information: <https://manned.org/unset>.
+
+- Remove the variable `foo`, or if the variable doesn't exist, remove the function `foo`:
+
+`unset {{foo}}`
+
+- Remove the variables foo and bar:
+
+`unset -v {{foo}} {{bar}}`
+
+- Remove the function my_func:
+
+`unset -f {{my_func}}`