Update the example PyTorch version in Installation doc

[pyf98]

Hi, I updated the example PyTorch and CUDA version in the installation doc to avoid confusion. Originally, the PyTorch version was 1.3.1, but according to #4038, it is no longer supported.

[codecov]

Codecov Report

Merging #4116 (bc08609) into master (640327b) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #4116   +/-   ##
=======================================
  Coverage   80.18%   80.18%           
=======================================
  Files         438      438           
  Lines       38012    38012           
=======================================
  Hits        30479    30479           
  Misses       7533     7533           

Flag	Coverage Δ
test_integration_espnet1	67.13% <ø> (ø)
test_integration_espnet2	52.06% <ø> (ø)
test_python	66.06% <ø> (ø)
test_utils	24.45% <ø> (ø)

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[sw005320]

Thanks!