fix: exists method raises error when no file found

[silentworks]

What kind of change does this PR introduce?

Bug fix

What is the current behavior?

.exists method is raising an exception when a file is not found

What is the new behavior?

.exists method is returning false when a file is not found

Additional context

Add any other context or screenshots.

[coveralls]

Pull Request Test Coverage Report for Build 12848405494

Details

• 6 of 10 (60.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.5%) to 83.709%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
storage3/_async/file_api.py	3	5	60.0%
storage3/_sync/file_api.py	3	5	60.0%

Totals
Change from base Build 12659581505:	-0.5%
Covered Lines:	483
Relevant Lines:	577

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 12848405494

Details

• 6 of 10 (60.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.5%) to 83.709%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
storage3/_async/file_api.py	3	5	60.0%
storage3/_sync/file_api.py	3	5	60.0%

Totals
Change from base Build 12659581505:	-0.5%
Covered Lines:	483
Relevant Lines:	577

---

💛 - Coveralls

[juancarlospaco]

LGTM