chore - remove isTest in SearchTextFieldAppBar Method

[Nanamare]

Issue

• close #666

Overview (Required)

• All UnitTests appear to succeed. I think it has been resolved naturally now.

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[github-actions[bot]]

Test Results

45 tests   45 :heavy_check_mark:  3m 48s :stopwatch:   9 suites    0 :zzz:   9 files      0 :x:

Results for commit ca80f1b1.

[takahirom]

May I ask if you checked PreviewTest?