Check argument types on `HTTP1.request/5`

[britto]

The same way we do in HTTP2.request/5. Noticed it through dialyzer while passing a map of headers instead of a list.

[coveralls]

Pull Request Test Coverage Report for Build 4749efbeb0e1fbcda004b00dd31258ca9aeb4ec8-PR-375

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage decreased (-0.06%) to 84.987%

---

Files with Coverage Reduction	New Missed Lines	%
test/support/mint/http1/test_server.ex	1	84.62%
<!--	Total:	1		-->

Totals
Change from base Build a947ca3e4c60d3bf0757ab457c465f949819ed71:	-0.06%
Covered Lines:	1319
Relevant Lines:	1552

---

💛 - Coveralls

[whatyouhide]

Thanks @britto 💟