Update lru requirement from 0.4.3 to 0.6.4

[dependabot-preview[bot]]

Updates the requirements on lru to permit the latest version.

Changelog

Sourced from lru's changelog.

v0.6.4 - 2020-02-03

• Fix memory leak when keys contain heap allocated data and ensure send/sync bounds apply to all conforming hashers.

v0.6.3 - 2020-12-19

• Fix memory leak in clear and resize methods.

v0.6.2 - 2020-12-12

• Rename optin_builtin_traits to auto_traits.

v0.6.1 - 2020-11-02

• Update dependency on hashbrown to 0.9.

v0.6.0 - 2020-08-02

• Update dependency on hashbrown to 0.8.

v0.5.3 - 2020-07-06

• Fix bug that causes crash when putting an item into a zero-capacity cache.

v0.5.2 - 2020-06-17

• Fix nightly feature.

v0.5.1 - 2020-06-02

• Fix memory leak whereby old entries wouldn't be dropped when cache is full.

v0.5.0 - 2020-05-28

• Stop gating the alloc crate behind the nightly flag.

v0.4.5 - 2020-05-25

• Use as_mut_ptr in drop to fix memory leak.

v0.4.4 - 2020-05-19

• Use mem::MaybeUninit for key and value fields of nodes and not the nodes themselves.

v0.4.3 - 2019-12-10

• Add back import of alloc crate on nightly which was accidentally removed.

v0.4.2 - 2019-12-08

... (truncated)

Commits

• 97d811a Merge pull request #106 from jeromefroe/jerome/prep-0.6.4-release
• 67cf7de Prep 0.6.4 release
• 5d35651 Merge pull request #105 from znly/zenly
• ec25be4 Merge pull request #104 from rafalmiel/fix_pop_leak
• a01f955 send/sync bounds should apply to all hashers
• ea64c8f Fix memory leak when using pop
• 0ba1a08 Merge pull request #102 from jeromefroe/prepare-0.6.3-release
• 0b2b5d6 Prepare 0.6.3 release
• 882db45 Merge pull request #101 from jeromefroe/jerome/fix-memory-leak-when-using-cle...
• 1294010 Use different atomic in each test case
• Additional commits viewable in compare view

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[dependabot-preview[bot]]

Superseded by #69.