Semicolon Cleanup

1. Semicolons were required in the wrong spot.
2. Make semicolons "invisible" (from the tree-sitter perspective).

Signed-off-by: Will Hawkins <hawkinsw@obs.cr>

tree-sitter-p4/test/corpus/transitions.txt

@@ -25,12 +25,10 @@ parser simple() {
        (identifier)
       )
      )
-     (semicolon)
     )
    )
   )
  )
- (semicolon)
 )
 
 =========================
@@ -74,15 +72,12 @@ parser simple() {
           (colon)
           (identifier)
          )
-         (semicolon)
         )
        )
       )
      )
-     (semicolon)
     )
    )
   )
  )
- (semicolon)
 )