Update redux requirement from ^4.0.0 to ^4.0.4 in /docs

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Updates the requirements on redux to permit the latest version.

Release notes

Sourced from redux's releases.

v4.0.4

This is a republish of 4.0.3 with an updated version of Babel to fix #3468

Changes

Commits

• 8aca937 4.0.4
• 5cbfdf9 Upgrade Babel to fix objectSpread2 bug
• d4ceb7e 4.0.3
• 0c3a2c7 Revert "Infer action types from combineReducers" (#3467)
• 5893473 4.0.2
• 4ae0352 Upgrade some deps
• a3aa378 Remove deprecated jsnext option
• d4075e1 docs: Fix fragment identifier (#3461)
• ff8fce0 Update UsageWithReactRouter.md (#3459)
• beb1fc2 removed distinctState() filter (#3450)
• Additional commits viewable in compare view

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