Clarify Grid Lines glossary definition (#31081)

* Update index.md

Grid lines are created by default even when we do not set the columns or rows explicitly. Therefore, it is more accurate to avoid stating that the grid lines are created when we use explicit grid.

* Update index.md

files/en-us/glossary/grid_lines/index.md

@@ -6,7 +6,7 @@ page-type: glossary-definition
 
 {{GlossarySidebar}}
 
-**Grid lines** are created when you define {{glossary("Grid tracks", "tracks")}} in the explicit grid using [CSS Grid Layout](/en-US/docs/Web/CSS/CSS_grid_layout).
+**Grid lines** are created anytime you use a [CSS Grid Layout](/en-US/docs/Web/CSS/CSS_grid_layout).
 
 ## Example