Fix equal operator (nushell#1561)

Author: sholderbach

lang-guide/chapters/operators.md

@@ -6,7 +6,7 @@
 - `-` - Minus / Subtraction
 - `*` - Multiply
 - `/` - Divide
-- `=` - Equal
+- `==` - Equal
 - `!=` - Not Equal
 - `//` - Floor Division
 - `<` - Less Than
@@ -47,4 +47,4 @@ TODO
 
 ### `[` and `]`
 
-### `{` and `}`
+### `{` and `}`