docs: Use 'Bank of Berlin' consistently in stopwords examples

Changed all references from 'Bank of America' to 'Bank of Berlin' for
consistency throughout the stopwords documentation in the notebook.

Updated 6 occurrences across:
- Example data (company_name field)
- Search query and comment
- Print statement
- Markdown explanation text

This addresses the GitHub Copilot feedback about inconsistent entity names.

Author: nkanu17

docs/user_guide/11_advanced_queries.ipynb

@@ -530,7 +530,7 @@
     "\n",
     "**When to use `STOPWORDS 0`:**\n",
     "- When you need to search for common words like \"of\", \"at\", \"the\"\n",
-    "- For entity names containing stopwords (e.g., \"Bank of America\", \"University of California\")\n",
+    "- For entity names containing stopwords (e.g., \"Bank of Berlin\", \"University of California\")\n",
     "- When working with structured data where every word matters"
    ]
   },
@@ -634,7 +634,7 @@
     "\n",
     "If we had used the default stopwords (not specifying `stopwords` in the schema), the word \"of\" would be filtered out during indexing. This means:\n",
     "\n",
-    "- ❌ Searching for `\"Bank of America\"` might not find exact matches\n",
+    "- ❌ Searching for `\"Bank of Berlin\"` might not find exact matches\n",
     "- ❌ The phrase would be indexed as `\"Bank America\"` (without \"of\")\n",
     "- ✅ With `STOPWORDS 0`, all words including \"of\" are indexed\n",
     "\n",