[calico] drop 3.18.x and make 3.21.x the new default (#8426)

roles/download/defaults/main.yml

@@ -93,7 +93,7 @@ github_image_repo: "ghcr.io"
 
 # TODO(mattymo): Move calico versions to roles/network_plugins/calico/defaults
 # after migration to container download
-calico_version: "v3.20.3"
+calico_version: "v3.21.2"
 calico_ctl_version: "{{ calico_version }}"
 calico_cni_version: "{{ calico_version }}"
 calico_flexvol_version: "{{ calico_version }}"
@@ -363,22 +363,18 @@ calicoctl_binary_checksums:
     v3.21.2: 0
     v3.20.3: 0
     v3.19.3: 0
-    v3.18.6: 0
   amd64:
     v3.21.2: d495edfc254e00f008ef6872422a31ef5f442a1ff96bcb724dd2df86ef75b7e3
     v3.20.3: 29bec97b1dfc135b830b0cbfd3dfe216f00e97e9e6ef08e620d81d4a09db6393
     v3.19.3: e9d91036764ec24f32025c3176efb2c2673b9936270e6165fb6583cce97bc43f
-    v3.18.6: 0306c2e82d7c77d53d3e1bc3d826c01bb670292562c1f2287b80738064710665
   arm64:
     v3.21.2: 94c1bec6b7661243f053314d901df54d2e3e5bf4eb746af09b29b07e4654f4b9
     v3.20.3: 63683f21515a20ceee8f234a9aba0e5efb342860940026d0ba6f281cc76aa1e3
     v3.19.3: ec3cfbd2dccbd614ac353be8c9abf8e336d8700fbd2b9b76da1c3c4c14a6dfe2
-    v3.18.6: 2990c2004d9b9ab6cfc913fe0ed521c12d7b5a3f3fcf4940549a8a15721e84dd
 calico_crds_archive_checksums:
   v3.21.2: 6f1342ac8b3d9ebfa9714f06aa92f4f0eea0d2b09d7e77ed73c0c9de0bb0aee8
   v3.20.3: 2a3a5cbe05c60fa2fc850252c4eecfa36dd6629191ed805eea31f9b5c740bc4c
   v3.19.3: 7066d0e6b0136920f82a75a5bd2d595e9f69bd3ab823403e920906569ec6be07
-  v3.18.6: f8eea12992c41bb4954364e9e4d332b4daf40305688973541110b6268dc0037a
 
 krew_archive_checksums:
   linux: