minor #8809 Fix diff syntax (michaelperrin)

This PR was merged into the 4.0 branch.

Discussion
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Fix diff syntax

Here is a PR similar to #8802 . I made a find & replace in all files and I think this is the only one left that needed to be fixed :)

There are some trailing whitespaces that got removed by my editor as well, but I think it's better not to have them.

Commits
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4a2c192 Fix diff syntax

Author: weaverryan

doctrine/associations.rst

@@ -445,7 +445,7 @@ it *is* possible, by writing clever methods. First, instead of a ``setProducts()
 method, create a ``addProduct()`` method::
 
     // src/Entity/Category.php
-    
+
     // ...
     class Category
     {
@@ -470,7 +470,7 @@ What about *removing* a ``Product`` from a ``Category``? Add a ``removeProduct()
 method::
 
     // src/Entity/Category.php
-    
+
     // ...
     class Category
     {
@@ -495,12 +495,12 @@ To make this work, you *now* need to allow ``null`` to be passed to ``Product::s
     {
         // ...
 
-        - public function getCategory(): Category
-        + public function getCategory(): ?Category
+    -     public function getCategory(): Category
+    +     public function getCategory(): ?Category
         // ...
 
-        - public function setCategory(Category $category)
-        + public function setCategory(Category $category = null)
+    -     public function setCategory(Category $category)
+    +     public function setCategory(Category $category = null)
         {
             $this->category = $category;
         }
@@ -514,7 +514,7 @@ to be *deleted* if it becomes "orphaned" (i.e. without a ``Category``)? To choos
 that behavior, use the `orphanRemoval`_ option inside ``Category``::
 
     // src/Entity/Category.php
-    
+
     // ...
 
     /**