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/bm

@@ -1,4 +1,4 @@
-#name : Benchmark.bmbm(...) do ... end
+# name: Benchmark.bmbm(...) do ... end
 # key: bm
 # --
 Benchmark.bmbm(${1:10}) do |x|