fix(deps): update dependency autoprefixer to v10.4.21

This MR contains the following updates:

Package	Type	Update	Change
autoprefixer	dependencies	patch	10.4.19 -> 10.4.21

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Release Notes

postcss/autoprefixer (autoprefixer)

v10.4.21

Compare Source

• Fixed old -moz- prefix for :placeholder-shown (by @​Marukome0743).

v10.4.20

Compare Source

• Fixed fit-content prefix for Firefox.

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