Remove csp-report.generate-csp-report.php.txt

It was added here:
https://chromium-review.googlesource.com/c/chromium/src/+/1108509

Every time I run the tests, it deletes this. I don't know why, but
it's a little annoying having to avoid committing it. So, I figure,
I should just try to commit it once and be done with it. :-)
I've learned that others are having the same issue, but maybe
aren't suffering as much as I am (I have a happy trigger finger
and often do git commit -a -m foo ...).

If this file is needed and you have an idea why, please enlighten
me and apologies for the attempt to remove it.

Thanks much!

Change-Id: I873211c98bc3158638c5abde59bc7acf060be8c7
Reviewed-on: https://chromium-review.googlesource.com/1152540Reviewed-by: Emil A Eklund <eae@chromium.org>
Reviewed-by: Xiaocheng Hu <xiaochengh@chromium.org>
Commit-Queue: Johannes Henkel <johannes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#578673}

third_party/WebKit/LayoutTests/http/tests/security/contentSecurityPolicy/resources/csp-report.generate-csp-report.php.txt

-CONTENT_TYPE: application/csp-report
-HTTP_REFERER: http://127.0.0.1:8000/security/contentSecurityPolicy/resources/generate-csp-report.php
-REQUEST_METHOD: POST
-=== POST DATA ===
-{"csp-report":{"document-uri":"http://127.0.0.1:8000/security/contentSecurityPolicy/resources/generate-csp-report.php","referrer":"","violated-directive":"script-src","effective-directive":"script-src","original-policy":"script-src 'self'; report-uri save-report.php?test=generate-csp-report.php","disposition":"enforce","blocked-uri":"inline","line-number":1,"source-file":"http://127.0.0.1:8000/security/contentSecurityPolicy/resources/generate-csp-report.php","status-code":200,"script-sample":""}}
\ No newline at end of file