Mark unsafe for Lint/RaiseException cop

Follow up #8169 (comment).

`Lint/RaiseException` cop is unsafe due to incompatibility
between bad and good cases.

## bad case

```console
% cat /tmp/example_for_exception.rb
begin
  raise Exception
rescue
  puts 'Handle exception'
end

% ruby example_for_exception.rb
example_for_exception.rb:2:in `<main>': Exception (Exception)
```

## good case

```console
% cat example_for_starndard_error.rb
begin
  raise StandardError
rescue
  puts 'Handle exception'
end

% ruby /tmp/example_for_starndard_error.rb
Handle exception
```

CHANGELOG.md

@@ -25,6 +25,7 @@
 
 * [#8146](https://github.com/rubocop-hq/rubocop/pull/8146): Use UTC in RuboCop todo file generation. ([@mauro-oto][])
 * [#8149](https://github.com/rubocop-hq/rubocop/pull/8149): Cop `Metrics/CyclomaticComplexity` now counts `&.`, `||=`, `&&=` and blocks known to iterate. Default bumped from 6 to 7. ([@marcandre][])
+* [#8178](https://github.com/rubocop-hq/rubocop/pull/8178): Mark unsafe for `Lint/RaiseException`. ([@koic][])
 
 ## 0.85.1 (2020-06-07)
 

config/default.yml

@@ -1620,6 +1620,7 @@ Lint/RaiseException:
   Description: Checks for `raise` or `fail` statements which are raising `Exception` class.
   StyleGuide: '#raise-exception'
   Enabled: pending
+  Safe: false
   VersionAdded: '0.81'
   AllowedImplicitNamespaces:
     - 'Gem'

docs/modules/ROOT/pages/cops_lint.adoc

@@ -2138,7 +2138,7 @@ rather than meant to be part of the resulting symbols.
 | Enabled by default | Safe | Supports autocorrection | VersionAdded | VersionChanged
 
 | Pending
-| Yes
+| No
 | No
 | 0.81
 | -