Change verify-rc-source-{{ target }}-macos-amd64 from macos-13 to macos-15-intel

Author: raulcd

dev/tasks/tasks.yml

@@ -358,7 +358,7 @@ tasks:
     template: verify-rc/github.macos.yml
     params:
       target: {{ target }}
-      github_runner: "macos-13"
+      github_runner: "macos-15-intel"
   {% endfor %}
 
   {% for target in ["cpp",
@@ -370,7 +370,6 @@ tasks:
     template: verify-rc/github.macos.yml
     params:
       env:
-        DO_NOTHING: 0
         ARROW_FLIGHT: 0
         ARROW_GANDIVA: 0
         PYTEST_ADDOPTS: "-k 'not test_cancellation'"