Upgrades the library "rand" version

[coveralls]

Pull Request Test Coverage Report for Build 529063685

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 11 unchanged lines in 4 files lost coverage.
• Overall coverage decreased (-0.02%) to 80.106%

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Files with Coverage Reduction	New Missed Lines	%
rsfbclient-native/src/connection.rs	1	73.49%
rsfbclient-rust/src/client.rs	3	79.37%
src/transaction/simple.rs	3	54.26%
src/connection/simple.rs	4	66.67%
<!--	Total:	11		-->

Totals
Change from base Build 444519206:	-0.02%
Covered Lines:	2875
Relevant Lines:	3589

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💛 - Coveralls