minor #20470 [TypeInfo] Fix PHP block (Korbeil)

This PR was merged into the 7.3 branch.

Discussion
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[TypeInfo] Fix PHP block

There is a missing `:` in TypeInfo documentation.
Here is a fix

Commits
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eb5ffa6 Fix PHP block in TypeInfo documentation

Author: javiereguiluz

components/type_info.rst

@@ -141,7 +141,7 @@ Checking a **simple type**::
     $type->isIdentifiedBy(DummyParent::class);     // true
     $type->isIdentifiedBy(DummyInterface::class);  // true
 
-Using callables for **complex checks**:
+Using callables for **complex checks**::
 
     class Foo
     {