[ruby-core:119152] [Ruby master Bug#20731] warning: mismatched indentations at 'when' appears with prism enabled ruby

Issue #20731 has been reported by yahonda (Yasuo Honda).

----------------------------------------
Bug #20731: warning: mismatched indentations at 'when' appears with prism enabled ruby
https://bugs.ruby-lang.org/issues/20731

* Author: yahonda (Yasuo Honda)
* Status: Open
* ruby -v: ruby 3.4.0dev (2024-09-12T20:03:28Z master 0fc8422a05) +PRISM [x86_64-linux]
* Backport: 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN
----------------------------------------
### Steps to reproduce
1. Create a `case_sample.rb` file
```
foo = :bar
case foo
  when :bar
    p 'foo is :bar'
  when :baz
    # do something
  else
    # do something
end
```
2. Run this file against the latest Ruby 3.4.0dev with -w option to show warnings
```
$ ruby -w case_sample.rb
```

### Expected behavior
It should show `"foo is :bar"` without any warnings as it runs against Ruby 3.3.5 or Ruby 3.4.0dev before prism is used by default

```
$ ruby -w case_sample.rb
"foo is :bar"
$ ruby -v
ruby 3.3.5 (2024-09-03 revision ef084cc8f4) [x86_64-linux]
$
```

```
$ ruby -w case_sample.rb
"foo is :bar"
$ ruby -v
ruby 3.4.0dev (2024-09-12T17:04:10Z master f2919bd11c) [x86_64-linux]
$
```

### Actual behavior
It raises `warning: mismatched indentations at 'when' with 'case' ` warnings as follows.
```
$ ruby -w case_sample.rb
case_sample.rb:3: warning: mismatched indentations at 'when' with 'case' at 2
case_sample.rb:5: warning: mismatched indentations at 'when' with 'case' at 2
"foo is :bar"
$ ruby -v
ruby 3.4.0dev (2024-09-12T20:03:28Z master 0fc8422a05) +PRISM [x86_64-linux]
$
```

### Background
This repro is based on the tzinfo code below.

https://github.com/tzinfo/tzinfo/blob/d5893c99bbcd842af86023f02a84fac1659b3031/lib/tzinfo/timestamp.rb#L115-L127
https://github.com/tzinfo/tzinfo/blob/d5893c99bbcd842af86023f02a84fac1659b3031/lib/tzinfo/timestamp.rb#L147-L154



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