Remove support for reserve commands. (#339)

### Description

Penultimate step of sunsetting the reserve commands.
https://forum.celo.org/t/sunset-of-reserve-commands/8454

### Other changes
 n/a

### Tested
n/a
### Related issues

- Fixes celo-org/celo-blockchain-planning#439

### Backwards compatibility

nope
### Documentation

docs for commands removed

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## PR-Codex overview
This PR removes the support for `reserve:*` commands in the CLI as part
of the deprecation process outlined in a forum discussion.

### Detailed summary
- Deleted the following files:
  - `packages/cli/src/commands/reserve/status.ts`
  - `packages/cli/src/commands/reserve/transfergold.ts`
  - `packages/cli/src/commands/reserve/transfergold.test.ts`
- Updated the `changeset/gold-pumas-fry.md` to reflect the major version
change for `@celo/celocli` and document the removal of `reserve:*`
commands.

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.changeset/gold-pumas-fry.md

@@ -0,0 +1,5 @@
+---
+'@celo/celocli': major
+---
+
+Remove support for reserve:\* commands. As foretold by https://forum.celo.org/t/sunset-of-reserve-commands/8454