[pantsd] Bump watchman version. (#5238)
[pantsd] Bump watchman version. (#5238)

Bump to the newer watchman 4.9.0.
baroquebobcat/pants,benjyw/pants,benjyw/pants,wisechengyi/pants,twitter/pants,tdyas/pants,jsirois/pants,benjyw/pants,wisechengyi/pants,pantsbuild/pants,tdyas/pants,pantsbuild/pants,baroquebobcat/pants,baroquebobcat/pants,tdyas/pants,wisechengyi/pants,UnrememberMe/pants,UnrememberMe/pants,baroquebobcat/pants,pantsbuild/pants,foursquare/pants,UnrememberMe/pants,pantsbuild/pants,twitter/pants,twitter/pants,twitter/pants,wisechengyi/pants,jsirois/pants,foursquare/pants,wisechengyi/pants,benjyw/pants,benjyw/pants,twitter/pants,tdyas/pants,foursquare/pants,baroquebobcat/pants,jsirois/pants,pantsbuild/pants,baroquebobcat/pants,UnrememberMe/pants,tdyas/pants,UnrememberMe/pants,UnrememberMe/pants,UnrememberMe/pants,baroquebobcat/pants,foursquare/pants,wisechengyi/pants,tdyas/pants,twitter/pants,twitter/pants,UnrememberMe/pants,wisechengyi/pants,tdyas/pants,foursquare/pants,benjyw/pants,foursquare/pants,tdyas/pants,tdyas/pants,benjyw/pants,foursquare/pants,wisechengyi/pants,baroquebobcat/pants,twitter/pants,foursquare/pants,wisechengyi/pants,baroquebobcat/pants,UnrememberMe/pants,foursquare/pants,pantsbuild/pants,twitter/pants,pantsbuild/pants