Remove use of eval() from ocr.py (#4481)

`eval(op_name)` -> `getattr(operators, op_name)`

### What problem does this PR solve?

Using `eval()` can lead to code injections and is entirely unnecessary
here.

### Type of change

- [x] Other (please describe):

Best practice code improvement, preventing the possibility of code
injection.

deepdoc/vision/ocr.py

@@ -19,6 +19,7 @@
 
 from api.utils.file_utils import get_project_base_directory
 from .operators import *  # noqa: F403
+from . import operators
 import math
 import numpy as np
 import cv2
@@ -55,7 +56,7 @@ def create_operators(op_param_list, global_config=None):
         param = {} if operator[op_name] is None else operator[op_name]
         if global_config is not None:
             param.update(global_config)
-        op = eval(op_name)(**param)
+        op = getattr(operators, op_name)(**param)
         ops.append(op)
     return ops