Merge pull request #7973 from DocFX/patch-1

Just a micro grammar update.

Author: lcobucci

docs/en/reference/annotations-reference.rst

@@ -99,7 +99,7 @@ Optional attributes:
 
 -  **length**: Used by the "string" type to determine its maximum
    length in the database. Doctrine does not validate the length of a
-   string values for you.
+   string value for you.
 
 -  **precision**: The precision for a decimal (exact numeric) column
    (applies only for decimal column), which is the maximum number of