fixed missing semicolon in documentation

docs/advanced.rst

@@ -10,7 +10,7 @@ present:
 
     #include <pybind11/pybind11.h>
 
-    namespace py = pybind11
+    namespace py = pybind11;
 
 Operator overloading
 ====================

docs/basics.rst

@@ -85,7 +85,7 @@ a file named :file:`example.cpp` with the following contents:
         return i + j;
     }
 
-    namespace py = pybind11
+    namespace py = pybind11;
 
     PYBIND_PLUGIN(example) {
         py::module m("example", "pybind11 example plugin");

docs/classes.rst

@@ -25,7 +25,7 @@ The binding code for ``Pet`` looks as follows:
 
     #include <pybind11/pybind11.h>
 
-    namespace py = pybind11
+    namespace py = pybind11;
 
     PYBIND_PLUGIN(example) {
         py::module m("example", "pybind11 example plugin");