Mention "no preceding space" rule for left paren in function declaration and lambda expressions

[muzimuzhi]

Currently this rule is mentioned in

• ‹app-args› in sec. 2.1.11.4 Application Expressions

  Note that there is no space allowed before the opening parenthesis of the application. https://pyret.org/docs/latest/Expressions.html#%28part._s~3aapp-expr%29

• ‹inst-expr› in sec. 2.1.11.7 Instantiation Expressions

  Spaces are not permitted before the left-angle bracket or after the right-angle bracket https://pyret.org/docs/latest/Expressions.html#%28part._s~3ainst-expr%29

But Pyret will also complain if a space exists before opening parenthesis in

• function declaration expressions like fun f (n): n end https://pyret.org/docs/latest/s_declarations.html#%28part._s~3afun-decl%29
• lambda expressions lam (n): n end https://pyret.org/docs/latest/Expressions.html#%28part._s~3alam-expr%29

This also seems to suggest, that the grammar rule for ‹args› (line 916 below) https://github.com/brownplt/pyret-docs/blob/e54e93331412615b27f8f5b3d54826e70a6f86a7/src/lang/forms.scrbl#L911-L916 should be updated to

args: PARENNOSPACE [list-arg-elt* binding] RPAREN

As a reference, in pyret-grammar.bnf in pyret-lang repo, ‹args› has grammar rule

args: (PARENNOSPACE|PARENAFTERBRACE) [binding (COMMA binding)*] RPAREN