Improve timetable list accessibility

[c0tt0n-candy]

Issue

• no issue

Overview (Required)

• I improved the accessibility of TimetableList.
  • When you enable TalkBack, startsTimeString and endsTimeString were being read separately, so now they are read as a whole.

Links

• Modifier.clearAndSetSemantics

Screenshot (Optional if screenshot test is present or unrelated to UI)

Before

After

[github-actions[bot]]

Test Results

210 tests   210 :heavy_check_mark:  6m 31s :stopwatch:   11 suites      0 :zzz:   11 files        0 :x:

Results for commit 9273b7cb.

[github-actions[bot]]

Snapshot diff report	File name	Image
TimetableScreenTest. checkLaunchAccessibi lityShot_compare.png