Fix content assist for method with Closure as last param and '{' as trigger character

[eric-milles]

Assuming Java Content Assist preference "Fill method arguments and show guessed arguments" is unchecked:

When a content assist proposal with a trailing closure -- like collect(Closure transform) -- is triggered with the { character, the current replacement is collect() {|, where | is the cursor position after insertion. To be consistent with other content assist modes, the replacement should be collect { | }.