build: fix access of issue number

---
type: pre_commit_static_analysis_report
description: Results of running static analysis checks when committing changes.
report:
  - task: lint_filenames
    status: passed
  - task: lint_editorconfig
    status: passed
  - task: lint_markdown
    status: na
  - task: lint_package_json
    status: na
  - task: lint_repl_help
    status: na
  - task: lint_javascript_src
    status: na
  - task: lint_javascript_cli
    status: na
  - task: lint_javascript_examples
    status: na
  - task: lint_javascript_tests
    status: na
  - task: lint_javascript_benchmarks
    status: na
  - task: lint_python
    status: na
  - task: lint_r
    status: na
  - task: lint_c_src
    status: na
  - task: lint_c_examples
    status: na
  - task: lint_c_benchmarks
    status: na
  - task: lint_c_tests_fixtures
    status: na
  - task: lint_shell
    status: na
  - task: lint_typescript_declarations
    status: na
  - task: lint_typescript_tests
    status: na
  - task: lint_license_headers
    status: passed
---

Author: Planeshifter

.github/workflows/slash_commands.yml

@@ -82,7 +82,7 @@ jobs:
               await github.rest.issues.createComment({
                 'owner': context.repo.owner,
                 'repo': context.repo.repo,
-                'issue_number': github.event.issue.number,
+                'issue_number': context.issue.number,
                 'body': `${quote}\n\n@${context.payload.comment.user.login}, slash command not recognized. Please use \`/stdlib help\` to view available commands.`
               });
             }