Fix convfact documentation (#571)

* Fix `convfact` documentation

* Update src/conversion.jl

Co-authored-by: Sebastian Stock <42280794+sostock@users.noreply.github.com>

* Add comma after e.g.

Co-authored-by: Sebastian Stock <42280794+sostock@users.noreply.github.com>

Author: JeffFessler

src/conversion.jl

@@ -1,6 +1,6 @@
 """
     convfact(s::Units, t::Units)
-Find the conversion factor from unit `t` to unit `s`, e.g. `convfact(m,cm) = 0.01`.
+Find the conversion factor from unit `t` to unit `s`, e.g., `convfact(m,cm) == 1//100`.
 """
 @generated function convfact(s::Units, t::Units)
     sunits = s.parameters[1]