Changed #1.0 to 1.0 in gallery-layout.ly stylesheet.

NOTE: LilyPond syntax changes now allow ...

    \override StemTremolo.beam-width = 1.5

... instead of ...

    \override StemTremolo.beam-width = #1.5

... (with the old pound sign).

Probably even more such simplifications are allowed. This commit changes strict
numeric RHS assignment only.