build: Fix line endings in update resources script
build: Fix line endings in update resources script

Used tr -d to remove line endings for external_revisions files in
update_external_sources.sh script.

Note: Also fixed comment

Change-Id: I9a467d60acc27eeced1f48e46c3bc5624c47ab23

KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools