[Objective-C] No longer ignore `xcworkspace` documents.
[Objective-C] No longer ignore `xcworkspace` documents.

Workspaces are real documents that can be opened, just like `xcodeproj`
documents. These documents are also generated/used by CocoaPods to
configure a project’s dependencies. For these reasons, there does not
seem a good reason to ignore these any longer.

chhsieh/gitTest_1,chhsieh/helloworld,bruennijs/ise.cppworkshop,hirochachacha/gitignore-generator,szymanskirafal/gitignore,szymanskirafal/gitignore,bruennijs/ise.cppworkshop,szymanskirafal/gitignore,bruennijs/ise.cppworkshop