Fix the NTP integration test (NTP website changed) (aws#1548)

### Issues:
N/A

### Description of changes: 
Fix the NTP integration test (NTP website changed).

Here is how the webpage looked like previously:
https://web.archive.org/web/20240104114229/https://www.ntp.org/downloads/.

Here is the new one: https://downloads.nwtime.org/ntp/

### Call-outs:
Point out areas that need special attention or support during the review
process. Discuss architecture or design changes.

### Testing:
How is this change tested (unit tests, fuzz tests, etc.)? Are there any
testing steps to be verified by the reviewer?

By submitting this pull request, I confirm that my contribution is made
under the terms of the Apache 2.0 license and the ISC license.

---------

Co-authored-by: dkostic <[email protected]>

tests/ci/integration/run_ntp_integration.sh

@@ -15,8 +15,15 @@ source tests/ci/common_posix_setup.sh
 
 # Assumes script is executed from the root of aws-lc directory
 SCRATCH_FOLDER="${SRC_ROOT}/NTP_BUILD_ROOT"
-NTP_DOWNLOAD_URL=$(curl -s https://www.ntp.org/downloads/ | grep -oP "\"https://archive.ntp.org/ntp.*?\.tar\.gz\"" | cut -d '"' -f2)
-NTP_TAR=$(echo "$NTP_DOWNLOAD_URL" | cut -d '/' -f6)
+NTP_WEBSITE_URL="https://downloads.nwtime.org/ntp/"
+
+# - curl fetches the HTML content of the website,
+# - the first grep searches for all occurrences of href attributes in anchor tags and outputs only the URLs,
+# - sed removes the href=" and trailing " from the URLs,
+# - the second grep filters only the links ending with .tar.gz,
+# - cut strips "/ntp/" from the link and retains only the tar name.
+NTP_TAR=$(curl -s ${NTP_WEBSITE_URL} | grep -o 'href="[^"]*"' | sed 's/href="//;s/"$//' | grep '.tar.gz$' | cut -d '/' -f3)
+NTP_DOWNLOAD_URL="${NTP_WEBSITE_URL}/${NTP_TAR}"
 NTP_SRC_FOLDER="${SCRATCH_FOLDER}/ntp-src"
 NTP_PATCH_FOLDER="${SRC_ROOT}/tests/ci/integration/ntp_patch"
 AWS_LC_BUILD_FOLDER="${SCRATCH_FOLDER}/aws-lc-build"