chore: add the missing frontmatter to some topics

01.curriculum/01.physics-chemistry-biology/03.niv3/02.geometrical-optics/01.geometrical-optics-general/02.geometrical-optics-validity/frontmatter.yaml

+# This page configuration is shared by all locales, in this directory.
+# You can override it in the individual frontmatter of the pages.
+
+content:
+    # https://learn.getgrav.org/15/content/collections#summary-of-collection-options
+    items: @self.children
+
+anchors:
+    active: false
\ No newline at end of file

01.curriculum/01.physics-chemistry-biology/03.niv3/02.geometrical-optics/frontmatter.yaml

+# This page configuration is shared by all locales, in this directory.
+# You can override it in the individual frontmatter of the pages.
+
+content:
+    # https://learn.getgrav.org/15/content/collections#summary-of-collection-options
+    items: @self.children
+
+anchors:
+    active: false
\ No newline at end of file