fix readme regarding port forwarding

[cbyrohl]

Adjusting the docs regarding port forwarding as

user@machine:~$ et -t "2222:2222" remote

works, while original readme's instructions fail with

user@machine:~$ et -t="2222:2222" remote
Exception: Argument ‘-t=2222:2222’ starts with a - but has incorrect syntax

Tested with et version 6.2.1

[codecov-commenter]

Codecov Report

Merging #522 (f53dc86) into master (113fb23) will increase coverage by 0.21%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #522      +/-   ##
==========================================
+ Coverage   71.22%   71.44%   +0.21%     
==========================================
  Files          49       49              
  Lines        3058     3050       -8     
==========================================
+ Hits         2178     2179       +1     
+ Misses        880      871       -9     

Impacted Files	Coverage Δ
src/base/PipeSocketHandler.cpp	73.07% <0.00%> (+0.70%)	⬆️
src/terminal/TerminalClient.cpp	42.12% <0.00%> (+0.90%)	⬆️
src/base/ServerClientConnection.cpp	96.42% <0.00%> (+3.57%)	⬆️

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[MisterTea]

Thanks!