minor #7025 Update buisness-logic (zairigimad)

This PR was submitted for the 3.1 branch but it was merged into the 2.7 branch instead (closes #7025).

Discussion
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Update buisness-logic

Replace all folders names with symfony3-project instead of  symfony2-project because symfony 2 and 3 don't have the same structure of folders .

Commits
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1ab78e0 Update buisness-logic

Author: wouterj

best_practices/business-logic.rst

@@ -15,7 +15,7 @@ Inside here, you can create whatever directories you want to organize things:
 
 .. code-block:: text
 
-    symfony2-project/
+    symfony-project/
     ├─ app/
     ├─ src/
     │  └─ AppBundle/
@@ -33,7 +33,7 @@ and put things there:
 
 .. code-block:: text
 
-    symfony2-project/
+    symfony-project/
     ├─ app/
     ├─ src/
     │  ├─ Acme/
@@ -176,7 +176,7 @@ The three entities defined by our sample blog application are a good example:
 
 .. code-block:: text
 
-    symfony2-project/
+    symfony-project/
     ├─ ...
     └─ src/
        └─ AppBundle/