Fix Vararg-UnionAll depwarn

[JackDunnNZ]

Prior to this change, when running with --depwarn=yes, this warning is shown during compilation:

WARNING: Wrapping `Vararg` directly in UnionAll is deprecated (wrap the tuple instead).

[codecov[bot]]

Codecov Report

Merging #476 (6b00b06) into master (d4f602f) will not change coverage. The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #476   +/-   ##
=======================================
  Coverage   85.41%   85.41%           
=======================================
  Files          26       26           
  Lines        1741     1741           
=======================================
  Hits         1487     1487           
  Misses        254      254           

Impacted Files	Coverage Δ
src/lanczos/lanczos.jl	100.00% <100.00%> (ø)

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[mkitti]

Thanks