Update pyopencl requirement from ~=2019.1.2 to ~=2021.2.6

[dependabot-preview[bot]]

Updates the requirements on pyopencl to permit the latest version.

Commits

• dfc4e84 Bump version to 2021.2.6
• f4b73fc Broadcast binary ops with device scalars (#502)
• a56281a docs: fix a few simple typos
• a3d0b5c Bump version to 2021.2.5
• a58fd72 Skip test_arithmetic_on_non_scalars if dataclasses is not importable
• d2db9ee Fix unbalanced angle bracket in pytest _ContextFactory
• 436a5cb Bump version to 2021.2.4
• b0dfbe0 test pyopencl arithmetic
• 78bedd8 correct pyopencl arithmetic to limit only for scalars
• eb0cbbb Drop Py2-only Array.nonzero (#494)
• Additional commits viewable in compare view

Dependabot will resolve any conflicts with this PR as long as you don't alter it yourself. You can also trigger a rebase manually by commenting @dependabot rebase.

---

Dependabot commands and options

You can trigger Dependabot actions by commenting on this PR:

• @dependabot rebase will rebase this PR
• @dependabot recreate will recreate this PR, overwriting any edits that have been made to it
• @dependabot merge will merge this PR after your CI passes on it
• @dependabot squash and merge will squash and merge this PR after your CI passes on it
• @dependabot cancel merge will cancel a previously requested merge and block automerging
• @dependabot reopen will reopen this PR if it is closed
• @dependabot close will close this PR and stop Dependabot recreating it. You can achieve the same result by closing it manually
• @dependabot ignore this major version will close this PR and stop Dependabot creating any more for this major version (unless you reopen the PR or upgrade to it yourself)
• @dependabot ignore this minor version will close this PR and stop Dependabot creating any more for this minor version (unless you reopen the PR or upgrade to it yourself)
• @dependabot ignore this dependency will close this PR and stop Dependabot creating any more for this dependency (unless you reopen the PR or upgrade to it yourself)
• @dependabot use these labels will set the current labels as the default for future PRs for this repo and language
• @dependabot use these reviewers will set the current reviewers as the default for future PRs for this repo and language
• @dependabot use these assignees will set the current assignees as the default for future PRs for this repo and language
• @dependabot use this milestone will set the current milestone as the default for future PRs for this repo and language
• @dependabot badge me will comment on this PR with code to add a "Dependabot enabled" badge to your readme

Additionally, you can set the following in your Dependabot dashboard:

• Update frequency (including time of day and day of week)
• Pull request limits (per update run and/or open at any time)
• Out-of-range updates (receive only lockfile updates, if desired)
• Security updates (receive only security updates, if desired)