fix: fix publish docs workflow

Author: lucasfang

.github/workflows/build_docs.yaml

@@ -48,7 +48,7 @@ jobs:
         run: |
           sudo apt-get update
           sudo apt-get install -y doxygen
-          make install-deps
+          pip install -r docs/requirements.txt
 
       - name: Build API
         run: |

docs/source/implementations/basic_concepts.rst

@@ -19,10 +19,10 @@
 .. https://github.com/apache/paimon/blob/master/docs/content/concepts/basic-concepts.md
 
 Basic Concepts
-=========================
+========================
 
 File Layouts
--------------------------
+------------------------
 All files of a table are stored under one base directory. Paimon files are
 organized in a layered style. The following image illustrates the file layout.
 Starting from a snapshot file, Paimon readers can recursively access all records