Update dependency buble to v0.19.6

[renovate]

This PR contains the following updates:

Package	Type	Update	Change	References
buble	dependencies	patch	0.19.4 -> 0.19.6	source

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Release Notes

Rich-Harris/buble

v0.19.6

Compare Source

• Fix class expressions with heritage in arrow functions (#​150)
• Support objectAssign: true in API as a short-hand for objectAssign: "Object.assign"
• Bundle all acorn dependencies (for now), but no others (#​159)

v0.19.5

Compare Source

• Transpile U+2028 and U+2029 according to stage 4 proposal json-superset
• Add /*@​__PURE__*/ annotations to transpiled classes
• Update support data
• Allow disabling spread properties transpiling
• Fix specific edge case with spread and computed properties (#​139)
• Allow global return statements
• Don't create unnecessary this aliases with loops (#​120)
• Don't allow getters and setters if IE8 is transpile target (#​20)

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[matticbot]

Test live: https://calypso.live/?branch=renovate/buble-0.x

[blowery]

We had this pinned in #27966 to fix a react-live dep. Need to check to see if this now works on devdocs.

[renovate]

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