[linalg.helpers.precond] Align note with [linalg.helpers.mandates]

Author: jensmaurer

source/numerics.tex

@@ -12077,7 +12077,7 @@
 
 \pnum
 \begin{note}
-These helpers use
+These exposition-only helper functions use
 the less constraining input concepts even for the output arguments,
 because the additional constraint for assignability of elements
 is not necessary, and