Deprecate release/0.1 (#218)

Divvi Up is converging its deployments to `draft-ietf-ppm-dap-09`, so we
no longer need to maintain the `release/0.1` branch. This commit removes
it from dependabot and updates the versions table in README.md.

Part of divviup/janus-ops#1856

.github/dependabot.yml

@@ -47,45 +47,3 @@ updates:
     schedule:
       interval: weekly
     target-branch: main
-
-  - package-ecosystem: gradle
-    directory: /
-    registries:
-      - google
-    schedule:
-      interval: weekly
-    groups:
-      agp:
-        patterns:
-          - com.android.application
-          - com.android.library
-      logback:
-        patterns:
-          - ch.qos.logback:*
-      jetpack:
-        patterns:
-          - androidx.*
-    target-branch: release/0.1
-
-  - package-ecosystem: cargo
-    directory: divviup/rust
-    schedule:
-      interval: weekly
-    ignore:
-      - dependency-name: prio
-        update-types:
-          - version-update:semver-minor
-      - dependency-name: janus_*
-        update-types:
-          - version-update:semver-minor
-    groups:
-      janus:
-        patterns:
-          - janus_*
-    target-branch: release/0.1
-
-  - package-ecosystem: github-actions
-    directory: /
-    schedule:
-      interval: weekly
-    target-branch: release/0.1

README.md

@@ -8,10 +8,10 @@ An Android client library for the [Distributed Aggregation Protocol][DAP].
 The following versions of the DAP protocol are supported by different branches
 and releases.
 
-| Package version | Git branch    | Protocol version                    | Conformant?                 | Status    |
-|-----------------|---------------|-------------------------------------|-----------------------------|-----------|
-| 0.1.0           | `release/0.1` | [`draft-ietf-ppm-dap-07`][draft-07] | Yes                         | Supported |
-| 0.2.0           | `main`        | [`draft-ietf-ppm-dap-09`][draft-09] | Yes                         | Supported |
+| Package version | Git branch    | Protocol version                    | Conformant? | Status    |
+|-----------------|---------------|-------------------------------------|-------------|-----------|
+| 0.1.0           | `release/0.1` | [`draft-ietf-ppm-dap-07`][draft-07] | Yes         | Unmaintained as of June 24, 2024 |
+| 0.2.0           | `main`        | [`draft-ietf-ppm-dap-09`][draft-09] | Yes         | Supported |
 
 [draft-07]: https://datatracker.ietf.org/doc/draft-ietf-ppm-dap/07/
 [draft-09]: https://datatracker.ietf.org/doc/draft-ietf-ppm-dap/09/