Update the format code for search, test=develop

doc/fluid/api/tensor/search.rst

+======
+search
+======
+
+..  toctree::
+    :maxdepth: 1
+
+    search/argmax.rst
+    search/argmin.rst
+    search/argsort.rst
+    search/has_inf.rst
+    search/has_nan.rst
+    search/index_sample.rst
+    search/index_select.rst
+    search/nonzero.rst
+    search/sort.rst
+    search/topk.rst
+    search/where.rst