chore: updating travis config to test on php 8.0

[Antnee]

No description provided.

[qlty-cloud-legacy]

Code Climate has analyzed commit cf8a177 and detected 0 issues on this pull request.

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[coveralls]

Pull Request Test Coverage Report for Build 83

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 100.0%

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Totals
Change from base Build 78:	0.0%
Covered Lines:	120
Relevant Lines:	120

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💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 83

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 100.0%

---

Totals
Change from base Build 78:	0.0%
Covered Lines:	123
Relevant Lines:	123

---

💛 - Coveralls

[Antnee]

No longer required, as Travis support has been removed from master on 7dbb0f2 #25