Keep snippet vars definitions in a single format across all snippets and documentation.

The format is:

# var-name: value

Previously snippets used a mixture of the following formatting:

#var-name: value
#var-name : value
# var-name: value
# var-name : value

snippets/ruby-mode/general/case

@@ -1,4 +1,4 @@
-#name : case ... end
+# name: case ... end
 # key: case
 # --
 case ${1:object}