Ignore wrong_self_convention clippy lint

    error: methods called `from_*` usually take no `self`
     --> impl/src/prop.rs:5:30
      |
    5 |     pub(crate) fn from_field(&self) -> Option<&Field> {
      |                              ^^^^^
      |
      = note: `-D clippy::wrong-self-convention` implied by `-D clippy::all`
      = help: consider choosing a less ambiguous name
      = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#wrong_self_convention

    error: methods called `from_*` usually take no `self`
      --> impl/src/prop.rs:51:30
       |
    51 |     pub(crate) fn from_field(&self) -> Option<&Field> {
       |                              ^^^^^
       |
       = help: consider choosing a less ambiguous name
       = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#wrong_self_convention

impl/src/lib.rs

@@ -8,7 +8,8 @@
     clippy::option_if_let_else,
     clippy::range_plus_one,
     clippy::single_match_else,
-    clippy::too_many_lines
+    clippy::too_many_lines,
+    clippy::wrong_self_convention
 )]
 
 extern crate proc_macro;