changed base image for AFNI to fedora:35 (#520)

* changed base image for AFNI to fedora:35

#519 (comment)

* Update examples.rst

forgot to change pkg-manager from apt to yum

* Update docs/user_guide/examples.rst

* Update docs/user_guide/examples.rst

---------

Co-authored-by: Jakub Kaczmarzyk <jakub.kaczmarzyk@gmail.com>

docs/user_guide/examples.rst

@@ -68,8 +68,8 @@ Docker
 .. code-block:: bash
 
     neurodocker generate docker \
-        --pkg-manager apt \
-        --base-image debian:buster-slim \
+        --pkg-manager yum \
+        --base-image fedora:35 \
         --afni method=binaries version=latest \
     > afni-binaries.Dockerfile
 
@@ -81,8 +81,8 @@ This does not install AFNI's R packages. To install relevant R things, use the f
 .. code-block:: bash
 
     neurodocker generate docker \
-        --pkg-manager apt \
-        --base-image debian:buster-slim \
+        --pkg-manager yum \
+        --base-image fedora:35 \
         --afni method=binaries version=latest install_r_pkgs=true \
     > afni-binaries-r.Dockerfile
 
@@ -95,8 +95,8 @@ Beware that this is AFNI's bleeding edge!
 .. code-block:: bash
 
     neurodocker generate docker \
-        --pkg-manager apt \
-        --base-image debian:buster-slim \
+        --pkg-manager yum \
+        --base-image fedora:35 \
         --afni method=source version=master \
     > afni-source.Dockerfile