Apply suggestions from code review

Co-authored-by: Kamil Tekiela <tekiela246@gmail.com>

Author: mmalferov

language/predefined/attributes/returntypewillchange.xml

@@ -15,7 +15,7 @@
    <simpara>
     Most non-final internal methods now require overriding methods to declare
     a compatible return type. Otherwise, a deprecation notice is emitted during
-    inheritance validation, warning that the signature violates covariance rules.
+    inheritance validation warning that the signature violates covariance rules.
    </simpara>
 
    <simpara>
@@ -41,8 +41,8 @@
     <simpara>
      The <classname>ReturnTypeWillChange</classname> attribute suppresses deprecation
      warnings <emphasis>only</emphasis> during the tentative return type phase.
-     After strict type checking is enforced, the attribute will stop working,
-     and a mismatch in an overriding method signature of an internal class
+     After strict type checking is enforced, the attribute will stop working
+     and a mismatch in the overriding method signature of an internal class
      will cause a fatal error.
     </simpara>
    </warning>