Fix tooltips for multiple params names on one line

[tlambert03]

another small bug fix when parsing tooltips from docs that have two parameters on one line, like:

"""
        Parameters
        ----------
        x, y : int
            Integers for you to use
"""

[codecov]

Codecov Report

Merging #120 (d80d8ff) into master (af729e2) will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #120      +/-   ##
==========================================
+ Coverage   90.25%   90.27%   +0.02%     
==========================================
  Files          25       25              
  Lines        2421     2427       +6     
==========================================
+ Hits         2185     2191       +6     
  Misses        236      236              

Impacted Files	Coverage Δ
magicgui/widgets/_function_gui.py	95.45% <100.00%> (+0.18%)	⬆️

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