Update deprecated aes_string() calls

[ssnn]

plotGmmThreshold(output, binwidth=0.02)
Warning messages:
1: aes_string() was deprecated in ggplot2 3.0.0.
ℹ Please use tidy evaluation ideoms with aes()
This warning is displayed once every 8 hours.
Call lifecycle::last_lifecycle_warnings() to see where this warning was generated.
2: Using size aesthetic for lines was deprecated in ggplot2 3.4.0.
ℹ Please use linewidth instead.
This warning is displayed once every 8 hours.
Call lifecycle::last_lifecycle_warnings() to see where this warning was generated.
3: The dot-dot notation (..density..) was deprecated in ggplot2 3.4.0.
ℹ Please use after_stat(density) instead.
This warning is displayed once every 8 hours.
Call lifecycle::last_lifecycle_warnings() to see where this warning was generated.

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[ssnn]

#443e4ac