Remove unused "Pfaffians" documentation node

Author: d-torrance

M2/Macaulay2/packages/Macaulay2Doc/ov_matrices.m2

@@ -26,7 +26,6 @@ document {
 	  "determinants and related computations",
 	  TO "rank of a matrix",
 	  TO "determinants and minors",
-	  TO "Pfaffians",
 	  TO "exterior power of a matrix",
 	  "display of matrices and saving matrices to a file",
 	  TO "format and display of matrices in Macaulay2",
@@ -640,12 +639,6 @@ document {
          },
      }
 
-document {
-     Key => "Pfaffians",
-     
-     SUBSECTION "pfaffians"
-     }
-
 document {
      Key => "exterior power of a matrix",
      "Since the ", TT "i", "-th exterior power is a functor, it applies