Deprecate prio 0.12, 0.15 (divviup#1084)

Divvi Up is converging all its deployments to the 0.7 series of Janus,
and so we no longer need to support our `draft-irtf-cfrg-vdaf-05` and
`-07` implementations. This commit stops dependabot updates for those
branches, drops them from `make-release`, and updates the versions table
in `README.md`.

Part of divviup/janus-ops#1856

.github/dependabot.yml

@@ -9,27 +9,3 @@ updates:
     directory: "/"
     schedule:
       interval: "weekly"
-
-  - package-ecosystem: "cargo"
-    directory: "/"
-    schedule:
-      interval: "weekly"
-    target-branch: release/0.15
-
-  - package-ecosystem: "github-actions"
-    directory: "/"
-    schedule:
-      interval: "weekly"
-    target-branch: release/0.15
-
-  - package-ecosystem: "cargo"
-    directory: "/"
-    schedule:
-      interval: "weekly"
-    target-branch: release/0.12
-
-  - package-ecosystem: "github-actions"
-    directory: "/"
-    schedule:
-      interval: "weekly"
-    target-branch: release/0.12

.github/workflows/make-release.yml

@@ -9,7 +9,7 @@ on:
           be marked as the latest release.
         required: false
         type: string
-        default: '["main","release/0.15","release/0.12"]'
+        default: '["main"]'
 
 jobs:
   bump-version:

README.md

@@ -38,10 +38,10 @@ increases (e.g., 0.10 to 0.11).
 | 0.9 | `release/0.9` | [`draft-irtf-cfrg-vdaf-03`][vdaf-03] | [`draft-ietf-ppm-dap-02`][dap-02] and [`draft-ietf-ppm-dap-03`][dap-03] | Yes | Unmaintained as of September 22, 2022 |
 | 0.10 | `release/0.10` | [`draft-irtf-cfrg-vdaf-03`][vdaf-03] | [`draft-ietf-ppm-dap-02`][dap-02] and [`draft-ietf-ppm-dap-03`][dap-03] | Yes | Unmaintained as of November 14, 2023 |
 | 0.11 | `release/0.11` | [`draft-irtf-cfrg-vdaf-04`][vdaf-04] | N/A | Yes | Unmaintained |
-| 0.12 | `release/0.12` | [`draft-irtf-cfrg-vdaf-05`][vdaf-05] | [`draft-ietf-ppm-dap-04`][dap-04] | Yes | Supported |
+| 0.12 | `release/0.12` | [`draft-irtf-cfrg-vdaf-05`][vdaf-05] | [`draft-ietf-ppm-dap-04`][dap-04] | Yes | Unmaintained as of June 24, 2024 |
 | 0.13 | `release/0.13` | [`draft-irtf-cfrg-vdaf-06`][vdaf-06] | [`draft-ietf-ppm-dap-05`][dap-05] | Yes | Unmaintained |
 | 0.14 | `release/0.14` | [`draft-irtf-cfrg-vdaf-06`][vdaf-06] | [`draft-ietf-ppm-dap-05`][dap-05] | Yes | Unmaintained |
-| 0.15 | `release/0.15` | [`draft-irtf-cfrg-vdaf-07`][vdaf-07] | [`draft-ietf-ppm-dap-07`][dap-07] | Yes | Supported |
+| 0.15 | `release/0.15` | [`draft-irtf-cfrg-vdaf-07`][vdaf-07] | [`draft-ietf-ppm-dap-07`][dap-07] | Yes | Unmaintained as of June 24, 2024 |
 | 0.16 | `main` | [`draft-irtf-cfrg-vdaf-08`][vdaf-08] | [`draft-ietf-ppm-dap-09`][dap-09] | Yes | Supported |
 
 [vdaf-01]: https://datatracker.ietf.org/doc/draft-irtf-cfrg-vdaf/01/