Update dependency @actions/core to v1.2.6

[mend-for-github-com]

This PR contains the following updates:

Package	Type	Update	Change
@actions/core (source)	dependencies	minor	1.0.0 -> 1.2.6

By merging this PR, the below vulnerabilities will be automatically resolved:

Severity	CVSS Score	CVE
Low	3.5	CVE-2020-15228

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Release Notes

actions/toolkit (@​actions/core)

v1.2.6

• Update exportVariable and addPath to use environment files

v1.2.5

• Correctly bundle License File with package

v1.2.4

• Be more lenient in accepting non-string command inputs
• Add Echo commands

v1.2.3

• IsDebug logging

v1.2.2

• Fix escaping for runner commands

v1.2.1

• Remove trailing comma from commands
• Add "types" to package.json

v1.2.0

• saveState and getState functions for wrapper tasks (on finally entry points that run post job)

v1.1.3

• setSecret added to register a secret with the runner to be masked from the logs
• exportSecret which was not implemented and never worked was removed after clarification from product.

v1.1.1

• Add support for action input variables with multiple spaces #​127
• Switched ## commands to :: commands (should have no noticeable impact) [#​110)(https://github.com/actions/toolkit/pull/110)

v1.1.0

Compare Source

• Added helpers for group and endgroup #​98

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