use full path for temporary filename

[olgabot]

In trim-low-abund.py, use the full path of the input filename rather than only the basename, in case of identical basenames which causes errors.

• Is any new functionality in tested? (This can be checked with
  make clean diff-cover or the CodeCov report that is automatically
  generated following a successful CI build.)
• Was a spellchecker run on the source code and documentation after
  changes were made?
• Have any changes to the command-line interface been explicitly described?
  Only backwards-compatible additions are allowed without a major version
  increment. Changing file formats also requires a major version number
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• Have any substantial changes been documented in CHANGELOG.md? See
  keepachangelog for more details.
• Do the changes respect streaming I/O? (Are they tested for streaming I/O?)

[codecov-io]

Codecov Report

Merging #1871 into master will not change coverage.
The diff coverage is 0%.

@@          Coverage Diff           @@
##           master   #1871   +/-   ##
======================================
  Coverage    0.07%   0.07%           
======================================
  Files          67      67           
  Lines        6685    6685           
  Branches     2487    2487           
======================================
  Hits            5       5           
  Misses       6680    6680

Impacted Files	Coverage Δ
scripts/trim-low-abund.py	0% <0%> (ø)	⬆️

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[standage]

Very concise solution to an annoying problem. Thanks!

[standage]

Closes #1870.

[standage]

Thanks for you contribution @olgabot!