Bump prompt-toolkit from 3.0.16 to 3.0.19

[dependabot-preview]

Bumps prompt-toolkit from 3.0.16 to 3.0.19.

Changelog

Sourced from prompt-toolkit's changelog.

3.0.19: 2021-06-17

Fixes:

• Make the flush method of the vt100 output implementation re-entrant (fixes an issue when using aiogevent).
• Fix off-by-one in FormattedTextControl mouse logic.
• Run print_container always in a thread (avoid interfering with possible event loop).
• Make sphinx autodoc generation platform agnostic (don't import Windows stuff when generating Sphinx docs).

3.0.18: 2021-03-22

New features:

• Added in_thread parameter to Application.run. This is useful for running an application in a background thread, while the main thread blocks. This way, we are sure not to interfere with an event loop in the current thread. (This simplifies some code in ptpython and fixes an issue regarding leaking file descriptors due to not closing the event loop that was created in this background thread.)

3.0.17: 2021-03-11

New features:

• Accept style parameter in print_container utility.
• On Windows, handle Control-Delete.

Fixes:

• Avoid leaking file descriptors in SSH server.

Commits

• b9a0ad9 Release 3.0.19
• cbaf059 Stricter types.
• eb525af Install types-contextvars in Github workflow.
• 594fb6f Make sphinx autodoc generation platform agnostic
• 71732aa Applied latest black (space around docstrings).
• b0083d0 Run print_container always in thread (avoid interfering with possible event l...
• c0cbff9 Document dont_extend_* parameters of Label
• 87cd853 Fix off-by-one in FormattedTextControl mouse logic
• bb5c5e6 Change prompt_async -> run_async
• c89cc2c pyperclip: Fix pyperclip selection type
• Additional commits viewable in compare view

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