ruby-smie-rules: Fix misindentation of a method call after assignment

* lisp/progmodes/ruby-mode.el (ruby-smie-rules): Fix indentation of a
method call after assignment with ruby-after-operator-indent=nil
(bug#61822).

* test/lisp/progmodes/ruby-mode-resources/ruby-after-operator-indent.rb:
Add corresponding example.

lisp/progmodes/ruby-mode.el

@@ -909,7 +909,9 @@ This only affects the output of the command `ruby-toggle-block'."
                      "<<=" ">>=" "&&=" "||=" "and" "or"))
      (cond
       ((not ruby-after-operator-indent)
-       (ruby-smie--indent-to-stmt ruby-indent-level))
+       (ruby-smie--indent-to-stmt (if (smie-indent--hanging-p)
+                                      ruby-indent-level
+                                    0)))
       ((and (smie-rule-parent-p ";" nil)
             (smie-indent--hanging-p))
        ruby-indent-level)))

test/lisp/progmodes/ruby-mode-resources/ruby-after-operator-indent.rb

@@ -10,6 +10,10 @@
 foo = obj.bar { |m| tee(m) } +
   obj.qux { |m| hum(m) }
 
+some_variable = abc + some_method(
+  some_argument
+)
+
 foo.
   bar
   .baz