typo in docs/source/installation.rst

[tomasohara]

The pip install command in the installation documentation incorrectly uses commas

$ grep pip.install docs/source/installation.rst | grep ,
    pip install buildozer, setuptools, cython==0.29.34

This leads to an error:

$ pip install buildozer, setuptools, cython==0.29.34
ERROR: Invalid requirement: 'buildozer,': Expected semicolon (after name with no version specifier) or end
    buildozer,

Note that the other cases don't use commas:

$ grep pip.install docs/source/installation.rst | grep -v ,
    pip install git+https://github.com/kivy/buildozer
    pip install legacy-cgi setuptools cython==0.29.34
    python3 -m pip install --user --upgrade buildozer # the --user should be removed if you do this in a venv
    python -m pip install --user --upgrade pip virtualenv kivy-ios

$ git describe --tags --dirty --always
1.5.0-131-g91ce81b