deprecate substitute_expression()

[burcin]

Symbolic expressions provide the method substitute_expression() which differs from substitute() by the fact that it can take several relations as arguments.

We should deprecate substitute_expression() and allow this call signature in substitute().

This is from the discussion at:

http://groups.google.com/group/sage-devel/msg/83d5a687c90dcc10

CC: @jpflori @kcrisman

Component: symbolics

Reviewer: Marc Mezzarobba

Issue created by migration from https://trac.sagemath.org/ticket/10048

[mezzarobba]

comment:6

Done in #12834.

[mezzarobba]

Reviewer: Marc Mezzarobba