[Docs] fixes problem with weird highlighting

Author: Pete Gleeson

docs/rules/extensions.md

@@ -8,13 +8,13 @@ In order to provide a consistent use of file extensions across your code base, t
 
 This rule either takes one string option, one object option, or a string and an object option. If it is the string `"never"` (the default value), then the rule forbids the use for any extension. If it is the string `"always"`, then the rule enforces the use of extensions for all import statements. If it is the string `"ignorePackages"`, then the rule enforces the use of extensions for all import statements except package imports.
 
-```json
+```
 "import/extensions": [<severity>, "never" | "always" | "ignorePackages"]
 ```
 
 By providing an object you can configure each extension separately.
 
-```json
+```
 "import/extensions": [<severity>, {
   <extension>: "never" | "always" | "ignorePackages"
 }]
@@ -24,7 +24,7 @@ By providing an object you can configure each extension separately.
 
 By providing both a string and an object, the string will set the default setting for all extensions, and the object can be used to set granular overrides for specific extensions.
 
-```json
+```
 "import/extensions": [
   <severity>,
   "never" | "always" | "ignorePackages",