Fix typo in mmil.html (gets->get) (#5013)

Author: jkingdon

mmil.raw.html

@@ -836,7 +836,7 @@
   If we have the coefficients of a polynomial, ~ elplyr gives explicit
   existence (in the form of a function definition) for a polynomial
   with those coefficients. But suppose we have a polynomial: can we
-  gets its coefficients? In the case of truncated existence, yes:
+  get its coefficients? In the case of truncated existence, yes:
   ~ elply2 does that.  But explicit existence in this case would be
   something like df-coe from set.mm.
 </li>