tests: mark tests 1631, 1632 flaky

We already marked them flaky in GHA/macos CI. They are also flaky in
other CI jobs, in other OSes, with multiple TLS backends:
- MSVC/LibreSSL: https://github.com/curl/curl/actions/runs/13683996410/job/38262956317
- MSVC/wolfSSL: https://github.com/curl/curl/actions/runs/13680682695/job/38252047077
- FreeBSD/OpenSSL3: https://github.com/curl/curl/actions/runs/13690910863/job/38283867721#step:3:1

Ref: fa461b4eff #14486

Closes #16584

.github/workflows/macos.yml

@@ -323,7 +323,6 @@ jobs:
             if [[ '${{ matrix.build.configure }}' = *'--with-secure-transport'* || \
                   '${{ matrix.build.generate }}' = *'-DCURL_USE_SECTRANSP=ON'* ]]; then
               TFLAGS+=' ~313'  # Secure Transport does not support crl file
-              TFLAGS+=' ~1631 ~1632'  # Secure Transport is not able to shutdown ftp over https gracefully yet
             fi
           fi
           source $HOME/venv/bin/activate

tests/data/test1631

@@ -3,6 +3,7 @@
 <keywords>
 FTP
 HTTPS-proxy
+flaky
 </keywords>
 </info>
 

tests/data/test1632

@@ -3,6 +3,7 @@
 <keywords>
 FTP
 HTTPS-proxy
+flaky
 </keywords>
 </info>