Deprecating lambdify decorator (#1823)

Deprecated `lambdify` decorator. The decorator is removed from
`pyccel/decorators.py` and the tests that use it are removed
(`tests/symbolic/scripts/lambdas.py`, and
`tests/symbolic/scripts/neural_net.py`)

---------

Co-authored-by: EmilyBourne <louise.bourne@gmail.com>

CHANGELOG.md

@@ -69,6 +69,7 @@ All notable changes to this project will be documented in this file.
 
 ### Deprecated
 
+-   #1820 : Deprecated unused decorator `@lambdify`
 -   #1786 : Remove support for `real` and `integer` as type annotations.
 -   #1812 : Stop allowing multiple main blocks inside a module.
 -   \[INTERNALS\] Remove property `ast.basic.TypedAstNode.precision`.

pyccel/decorators.py

@@ -13,7 +13,6 @@
     'bypass',
     'elemental',
     'inline',
-    'lambdify',
     'private',
     'pure',
     'stack_array',
@@ -22,16 +21,6 @@
     'types',
 )
 
-def lambdify(f):
-
-    args = f.__code__.co_varnames
-    from sympy import symbols
-    args = symbols(args)
-    expr = f(*args)
-    def wrapper(*vals):
-        return  expr.subs(zip(args,vals)).doit()
-
-    return wrapper
 
 def sympy(f):
     return f