stash: Remove old versions (#22201)

This PR removes versions of the Stash that were introduced in `v0.67` or
older, the current production release is `v0.71`.

### Motivation

Reduces build and test times of the `mz_stash` crate.

### Checklist

- [ ] This PR has adequate test coverage / QA involvement has been duly
considered.
- [ ] This PR has an associated up-to-date [design
doc](https://github.com/MaterializeInc/materialize/blob/main/doc/developer/design/README.md),
is a design doc
([template](https://github.com/MaterializeInc/materialize/blob/main/doc/developer/design/00000000_template.md)),
or is sufficiently small to not require a design.
  <!-- Reference the design in the description. -->
- [ ] If this PR evolves [an existing `$T ⇔ Proto$T`
mapping](https://github.com/MaterializeInc/materialize/blob/main/doc/developer/command-and-response-binary-encoding.md)
(possibly in a backwards-incompatible way), then it is tagged with a
`T-proto` label.
- [ ] If this PR will require changes to cloud orchestration or tests,
there is a companion cloud PR to account for those changes that is
tagged with the release-blocker label
([example](MaterializeInc/cloud#5021)).
<!-- Ask in #team-cloud on Slack if you need help preparing the cloud
PR. -->
- [x] This PR includes the following [user-facing behavior
changes](https://github.com/MaterializeInc/materialize/blob/main/doc/developer/guide-changes.md#what-changes-require-a-release-note):
  - N/a

src/stash/protos/hashes.json

@@ -3,46 +3,6 @@
     "name": "objects.proto",
     "md5": "bef6b30952d5e77b7bfd2bebe0fe23ae"
   },
-  {
-    "name": "objects_v25.proto",
-    "md5": "0a055b56539327ccbb8e23f209843cf2"
-  },
-  {
-    "name": "objects_v26.proto",
-    "md5": "bffd4936bea8f4f894662fcea12e4a5d"
-  },
-  {
-    "name": "objects_v27.proto",
-    "md5": "7ccd2c67b302d72cc4c94be892c7cfc1"
-  },
-  {
-    "name": "objects_v28.proto",
-    "md5": "891db1de528b10e073463cb8108556e0"
-  },
-  {
-    "name": "objects_v29.proto",
-    "md5": "a79ba1c1f4536c945ac6ee26fcc38946"
-  },
-  {
-    "name": "objects_v30.proto",
-    "md5": "85e44d81055146392f272df16d40e92e"
-  },
-  {
-    "name": "objects_v31.proto",
-    "md5": "e78e005dc9ddef0dd00cd5a580d222c6"
-  },
-  {
-    "name": "objects_v32.proto",
-    "md5": "5cedf06f7ee9f15a6ada28067907639b"
-  },
-  {
-    "name": "objects_v33.proto",
-    "md5": "b5f70889965589369efc18ec36e8cbd8"
-  },
-  {
-    "name": "objects_v34.proto",
-    "md5": "cddbbfecec523eec8a9f685633fb5c7c"
-  },
   {
     "name": "objects_v35.proto",
     "md5": "7d989b1afbbf906cb6fcc72fab67aba2"