Fix Wrapper Documentation. (pyccel#1870)

Correct a small issue in the wrapper documentation : 
From : 
```python
def _print_ClassName(self, stmt):
    ...
    return Y
```
To : 
```python
def _wrap_ClassName(self, stmt):
    ...
    return Y
```

Co-authored-by: mustapha-belbiad <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>

Author: mustapha-belbiad

developer_docs/wrapper_stage.md

@@ -20,7 +20,7 @@ The entry point for the class `Wrapper` is the function `wrap`.
 The `_wrap` function internally calls a function named `_wrap_X`, where `X` is the type of the object.
 These functions must have the form:
 ```python
-def _print_ClassName(self, stmt):
+def _wrap_ClassName(self, stmt):
     ...
     return Y
 ```