GH-38921:[CI] Fix spelling (#38922)

### Rationale for this change

### What changes are included in this PR?

Spelling fixes to .github/

### Are these changes tested?

### Are there any user-facing changes?

* Closes: #38921

Authored-by: Josh Soref <2119212+jsoref@users.noreply.github.com>
Signed-off-by: Sutou Kouhei <kou@clear-code.com>

.github/workflows/comment_bot.yml

@@ -46,7 +46,7 @@ jobs:
           python-version: 3.8
       - name: Install Archery and Crossbow dependencies
         run: pip install -e arrow/dev/archery[bot]
-      - name: Handle Github comment event
+      - name: Handle GitHub comment event
         env:
           ARROW_GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
           CROSSBOW_GITHUB_TOKEN: ${{ secrets.CROSSBOW_GITHUB_TOKEN }}

.github/workflows/dev_pr/issue_check.js

@@ -103,7 +103,7 @@ async function commentNotStartedTicket(github, context, pullRequestNumber) {
 }
 
 /**
- * Assigns the Github Issue to the PR creator.
+ * Assigns the GitHub Issue to the PR creator.
  *
  * @param {Object} github
  * @param {Object} context

.github/workflows/issue_bot.yml

@@ -64,7 +64,7 @@ jobs:
               "per_page": 100,
             });
 
-            // this removes non-existent labels
+            // this removes nonexistent labels
             component_labels = component_labels.filter(
               label => repo_labels.data.some(repo_label => repo_label.name === label)
             );