Fix otel-collector-windows packaging script

- PR #360 changed the otel-collector-windows packaging script to use
  Windows-style backslashes as path delimiters
- This isn't actually desirable because this line exists to prevent an
  error when exporting a BOSH release and attempting to compile this
  Windows package on a Linux instance

Fixes:
  .exiter.ps1: No such file or directory

packages/otel-collector-windows/packaging

@@ -1,4 +1,4 @@
-. .\exiter.ps1
+. ./exiter.ps1
 . C:\var\vcap\packages\golang-1.20-windows\bosh\compile.ps1
 $env:CGO_ENABLED="0"