DOC: Modify Raises section (#3226)

Author: j-t-1

pypdf/_doc_common.py

@@ -343,8 +343,7 @@ def get_num_pages(self) -> int:
             The number of pages of the parsed PDF file.
 
         Raises:
-            PdfReadError: if file is encrypted and restrictions prevent
-                this action.
+            PdfReadError: If restrictions prevent this action.
 
         """
         # Flattened pages will not work on an encrypted PDF;