Revert "Suppress pip warning about installing scripts not in PATH"

This reverts commit 2eaa7a21b0 because the
--no-warn-script-location option only exists in Python 3.9+ apparently
and we don't want to require such a new version just for this.

appveyor.yml

@@ -74,7 +74,7 @@ build_script: c:\projects\wxwidgets\build\tools\appveyor.bat
 before_test:
 - ps: |
     Write-Output "Getting and launching httpbin."
-    C:\Python35\Scripts\pip.exe --disable-pip-version-check --no-warn-script-location install httpbin
+    C:\Python35\Scripts\pip.exe --disable-pip-version-check install httpbin
     Start-Job -Name wx_httpbin { C:\Python35\python.exe -m httpbin.core 2>&1 > c:\projects\wxwidgets\httpbin.log }
     Start-Sleep -Seconds 5
     if (curl -s http://127.0.0.1:5000/ip > $null) {