🌱 Improve search commit e2e tests

[naveensrinivasan]

• Add 2 tests for searching commits in e2e/searchCommits_test.go
• Fix errors in e2e/searchCommits_test.go when not using HEAD or when user does not exist

[e2e/searchCommits_test.go]

• Add 2 tests for searching commits
• Fix error when not using HEAD
• Fix error when user does not exist

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[codecov]

Codecov Report

Merging #3295 (babc990) into main (a779588) will decrease coverage by 11.05%.
The diff coverage is n/a.

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #3295       +/-   ##
===========================================
- Coverage   72.18%   61.14%   -11.05%     
===========================================
  Files         173      173               
  Lines       12686    12686               
===========================================
- Hits         9158     7757     -1401     
- Misses       3025     4502     +1477     
+ Partials      503      427       -76     

[spencerschrock]

Alternatively, these could probably be hooked up to a stub http.RoundTripper and avoid the need for downloading altogether.
Similar to what we do in the webhooks test:

scorecard/clients/githubrepo/webhook_test.go

Lines 71 to 89 in cc55b36

	httpClient := &http.Client{
	Transport: stubTripper{
	responsePath: tt.responsePath,
	},
	}
	client := github.NewClient(httpClient)
	handler := &webhookHandler{
	ghClient: client,
	ctx: ctx,
	}
	repoURL := repoURL{
	owner: "ossf-tests",
	repo: "foo",
	commitSHA: clients.HeadSHA,
	}
	handler.init(ctx, &repoURL)
	got, err := handler.listWebhooks()
	if (err != nil) != tt.wantErr {