Make method name consistent in embedded video component

We were using `reg_exp` as the method name, when it returned
`VIMEO_REGEX` or `YOUTUBE_REGEX`.

So using `regex` as the method name is less confusing.

app/components/shared/embedded_video_component.rb

@@ -33,7 +33,7 @@ class Shared::EmbeddedVideoComponent < ApplicationComponent
       end
     end
 
-    def reg_exp
+    def regex
       if server == "Vimeo"
         record.class::VIMEO_REGEX
       elsif server == "YouTube"
@@ -50,7 +50,7 @@ class Shared::EmbeddedVideoComponent < ApplicationComponent
     end
 
     def match
-      @match ||= link.match(reg_exp) if reg_exp
+      @match ||= link.match(regex) if regex
     end
 
     def iframe_attributes