Update changelog

Author: nikic

package.xml

@@ -23,7 +23,13 @@
  </stability>
  <license uri="https://github.com/nikic/php-ast/blob/master/LICENSE">BSD-3-Clause</license>
  <notes>
-- TBD
+This release is the same as version 0.1.7 with obsolete and deprecated functionality removed.
+
+- Removed AST versions prior to version 50.
+- Removed ast\Node\Decl class, which is no longer used.
+- Removed AST kinds AST_AND, AST_COALESCE, AST_GREATER, AST_GREATER_EQUAL, AST_OR, AST_SILENCE,
+  AST_UNARY_MINUS, and AST_UNARY_PLUS, which are no longer used.
+- Removed ASSIGN_* AST flags, which are no longer used.
  </notes>
  <contents>
   <dir name="/">
@@ -40,7 +46,6 @@
     <file name="php_ast.h" role="src" />
     <dir name="tests">
       <file name="001.phpt" role="test" />
-      <file name="002.phpt" role="test" />
       <file name="array_destructuring_old.phpt" role="test" />
       <file name="array_destructuring.phpt" role="test" />
       <file name="assign_ops.phpt" role="test" />