Fix bad method links in docstrings (#13471)

# Description

Seems like I developed a bit of a bad habit of trying to link

```rust
/// [`.foo()`]
```

in docstrings, and this just doesn't work automatically; you have to do 

```rust
/// [`.foo()`](Self::foo)
```

if you want it to actually link. I think I found and replaced all of
these.

# User-Facing Changes

Just docs.

crates/nu-engine/src/compile/builder.rs

@@ -423,7 +423,7 @@ impl BlockBuilder {
         self.push(Instruction::Jump { index: label_id.0 }.into_spanned(span))
     }
 
-    /// The index that the next instruction [`.push()`]ed will have.
+    /// The index that the next instruction [`.push()`](Self::push)ed will have.
     pub(crate) fn here(&self) -> usize {
         self.instructions.len()
     }