fix(docs): update changed component theme vars link (#1550)

docs/articles/migration/350-400.md

@@ -194,14 +194,14 @@ For those variables that are removed, you can create custom local variables unde
 Starting with Nebular 4.0 we will be moving to restrict direct modification of component variables through theme interface, making those private internal implementations.
 We believe that flexibility provided by the themes variables will allow achieving smaller and better changes of the look&feel without modifying specific component theme variables.    
 But in a case when you modified component theme variables, e.g. `card-bg`, `header-fg`, and need those changes, make the change in accordance with the 
-[Components variables changes in Nebular 4.0.0](https://github.com/akveo/nebular/tree/master/src/framework/theme/350-400-components-variables-changes.md) doc.
+[Components variables changes in Nebular 4.0.0](https://github.com/akveo/nebular/tree/master/src/framework/theme/350-400-component-variables-changes.md) doc.
 
 
 6) Fix all `nb-theme(NON-EXISTING-VAR)` calls.
 
 In case you used `nb-theme` calls in your scss files directly accessing theme or component variables, you would need to fix those calls to reference new theme variables.
 You can follow both [Theme variables change in Nebular 4.0.0](https://github.com/akveo/nebular/tree/master/src/framework/theme/350-400-theme-variables-changes.md) and 
-[Components variables changes in Nebular 4.0.0](https://github.com/akveo/nebular/tree/master/src/framework/theme/350-400-components-variables-changes.md) docs to make a better decision on what should be changed to what.
+[Components variables changes in Nebular 4.0.0](https://github.com/akveo/nebular/tree/master/src/framework/theme/350-400-component-variables-changes.md) docs to make a better decision on what should be changed to what.
 
 At the end - check your console output - it should not contain any sass warning.