refactor: set strconv.ParseFloat bitsize to 64

[lilasxie]

strconv.ParseFloat will always treat bizSize parameter as 64 if we don't set it to 32, it's odd to set it to 0, although this won't affect the result

[coveralls]

Pull Request Test Coverage Report for Build 6898626179

Warning: This coverage report may be inaccurate.

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A quick fix for this PR: rebase it; your next report should be accurate.

• 1 of 1 (100.0%) changed or added relevant line in 1 file are covered.
• 85 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.2%) to 56.07%

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Files with Coverage Reduction	New Missed Lines	%
rpcclient/infrastructure.go	85	39.08%

Totals
Change from base Build 6871622756:	-0.2%
Covered Lines:	27953
Relevant Lines:	49854

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💛 - Coveralls

[halseth]

LGTM