minor improvements to the normalization chapter

Author: dimitri-yatsenko

book/30-schema-design/055-normalization.ipynb

@@ -23,7 +23,7 @@
       "cell_type": "markdown",
       "metadata": {},
       "source": [
-        "## Approach 1: Mathematical Normalization (Codd's Normal Forms)\n",
+        "## Approach 1: Mathematical Normalization\n",
         "\n",
         "Edgar F. Codd developed formal normalization theory in the early 1970s, rooted in the mathematical foundations of the relational model [@10.1145/358024.358054]. This approach is deeply tied to predicate calculus and the original conceptualization of relations.\n",
         "\n",
@@ -265,7 +265,7 @@
       "cell_type": "markdown",
       "metadata": {},
       "source": [
-        "## Approach 2: Entity Normalization (Chen's Entity-Relationship Model)\n",
+        "## Approach 2: Entity Normalization\n",
         "\n",
         "In 1976, Peter Chen introduced the Entity-Relationship Model [@10.1145/320434.320440], which revolutionized how we think about database design. Rather than starting with predicates, attributes, and functional dependencies, Chen proposed starting with **entities** and **relationships**.\n",
         "\n",