Corrected port for Matrix Plugin

[caronc]

Description:

Related issue (if applicable): n/a

A small bug with the Matrix plugin prevented it from generating the proper upstream URL when no port is specified.

Checklist

• The code change is tested and works locally.
• There is no commented out code in this PR.
• No lint errors (use flake8)
• 100% test coverage

Testing

Anyone can help test this source code as follows:

# Create a virtual environment to work in as follows:
python3 -m venv apprise

# Change into our new directory
cd apprise

# Activate our virtual environment
source bin/activate

# Install the branch
pip install git+https://github.com/caronc/apprise.git@matrix-cleanup

# Test out the changes with the following command:
apprise -t "Test Title" -b "Test Message" \
  "matrixs://mylocalserver/#channel"

[codecov-commenter]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (2b57c5d) 99.98% compared to head (f1fba47) 99.98%.

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Additional details and impacted files

@@           Coverage Diff           @@
##           master     #900   +/-   ##
=======================================
  Coverage   99.98%   99.98%           
=======================================
  Files         120      120           
  Lines       15996    15997    +1     
  Branches     3268     3268           
=======================================
+ Hits        15994    15995    +1     
  Misses          1        1           
  Partials        1        1           

Impacted Files	Coverage Δ
apprise/plugins/NotifyMatrix.py	100.00% <100.00%> (ø)

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