Remove context keyword from security handlers

[Ruwann]

Follow-up on #1671

Since the request context is available globally, we can remove this complexity from the security handlers ("There should be one-- and preferably only one --obvious way to do it.")

In addition it seems like there weren't any tests for the context in security handler functions, and I don't think there's a lot of value in a test for checking the context in security functions specifically.

[coveralls]

Pull Request Test Coverage Report for Build 4767722029

• 0 of 4 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.04%) to 93.945%

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Totals
Change from base Build 4763817389:	0.04%
Covered Lines:	3305
Relevant Lines:	3518

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💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 4767722029

• 4 of 4 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.04%) to 93.945%

---

Totals
Change from base Build 4763817389:	0.04%
Covered Lines:	3305
Relevant Lines:	3518

---

💛 - Coveralls

[RobbeSneyders]

Thx @Ruwann!
So should we do this for the view functions as well?

[Ruwann]

I think it would indeed make sense to also do it for the view functions as well. I haven't found the reasoning for adding it but the same argument applies: one way of accessing the context instead of two.

For the security handlers, the context argument was added in #869 but not really clear what the reason was - I assume it was because it was the easiest (?) way of making the context available for aiohttp in security handler functions?