Update 02_SIGNALduino_calcRSSI.t - PERL WARNING eliminated

[HomeAutoUser]

• Please check if the PR fulfills these requirements

• Tests for the changes have been added / modified (needed for for bug fixes / features)
• commandref has been added / updated (needed for bug fixes / features)

• What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)

• Bugfix (please link issue)
• Feature enhancement
• Documentation update
• Unittest enhancement
• other

• What is the current behavior?
  (You can also link to an open issue here, if this describes the current behavior)
  2021-09-01T15:48:48.8853674Z ##[error]2021.09.01 15:48:44 1: PERL WARNING: "my" variable $rssi masks earlier declaration in same scope at /home/runner/work/RFFHEM/RFFHEM/t/FHEM/00_SIGNALduino/02_SIGNALduino_calcRSSI.t line 47.

• What is the new behavior (if this is a feature change)?
  no PERL WARNING

• Does this PR introduce a breaking change? (What changes might users need to make in their application due to this PR?)
  no

• Other information:

[codecov]

Codecov Report

Merging #1014 (cd7005a) into master (a07524a) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1014   +/-   ##
=======================================
  Coverage   50.04%   50.04%           
=======================================
  Files         218      218           
  Lines       15276    15276           
  Branches     2856     2856           
=======================================
  Hits         7645     7645           
  Misses       5995     5995           
  Partials     1636     1636           

Flag	Coverage Δ
fhem	50.24% <ø> (ø)
modules	50.04% <ø> (ø)
perl	51.00% <ø> (ø)
unittests	50.04% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
t/FHEM/00_SIGNALduino/02_SIGNALduino_calcRSSI.t	100.00% <ø> (ø)

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