DOC change cos7 instructions

Author: beckermr

src/maintainer/knowledge_base.rst

@@ -1065,23 +1065,13 @@ put the following in your build section.
        - {{ compiler('c') }}
        - sysroot_linux-64 2.17  # [linux64]
 
-You also need to use a newer docker image by setting the following in the ``conda_build_config.yaml``
+You also need to use a newer docker image by setting the following in the ``conda-forge.yml``
 of your recipe and rerendering.
 
 .. code-block:: yaml
 
-   cudnn:                                    # [linux64]
-     - undefined                             # [linux64]
-   cuda_compiler_version:                    # [linux64]
-     - None                                  # [linux64]
-   docker_image:                             # [linux64]
-     - condaforge/linux-anvil-cos7-x86_64    # [linux64]
-   cdt_name:                                 # [linux64]
-     - cos7                                  # [linux64]
-
-The extra ``cuda_compiler_version`` key is needed because we currently zip that
-key with ``docker_image``. Also ``cdt_name`` ensures the CDTs match the CentOS
-version. If this changes in the future, then this extra key may not be needed.
+   os_version:
+     linux_64: cos7
 
 Finally, note that the ``aarch64`` and ``ppc64le`` platforms already use CentOS 7.