Remove support for the Cedar-14 stack (#1110)

Since the stack is end of life and builds have been disabled:
https://devcenter.heroku.com/changelog-items/1943

There are only two temporarily exempted customers using Python, who
can switch to the Cedar-14 support branch if they still need to build
their Python apps (most of which haven't been built recently).

Closes @W-8054727@.

test/run-features

@@ -80,10 +80,6 @@ testPipenvPythonVersion2_7() {
 }
 
 testPipenvPythonFullVersion() {
-  # Python 3.7+ requires newer libssl than is present on Cedar-14.
-  if [[ "${STACK}" = "cedar-14" ]]; then
-    return
-  fi
   compile "pipenv-full-version"
   assertCaptured "3.7.8"
   # Can't use `assertCapturedSuccess` since stderr contains:
@@ -140,7 +136,7 @@ testHooks() {
     SOME_APP_CONFIG_VAR
     STACK
   )
-  if [[ "${STACK}" == "cedar-14" || "${STACK}" == "heroku-16" ]]; then
+  if [[ "${STACK}" == "heroku-16" ]]; then
     # Remove "OLDPWD" from expected_env_vars since for bash <4.4 it's not exported to subshells:
     # https://github.com/heroku/heroku-buildpack-python/pull/1011#issuecomment-665117835
     read -ra expected_env_vars <<< "${expected_env_vars[@]/OLDPWD/}"

test/run-versions

@@ -112,10 +112,6 @@ testPython3_6_warn() {
 }
 
 testPython3_7() {
-  # Python 3.7+ requires newer libssl than is present on Cedar-14.
-  if [[ "${STACK}" = "cedar-14" ]]; then
-    return
-  fi
   compile "python3_7"
   assertCaptured "Installing ${LATEST_37}"
   assertNotCaptured "security update"
@@ -125,10 +121,6 @@ testPython3_7() {
 }
 
 testPython3_7_warn() {
-  # Python 3.7+ requires newer libssl than is present on Cedar-14.
-  if [[ "${STACK}" = "cedar-14" ]]; then
-    return
-  fi
   compile "python3_7_warn"
   assertCaptured "Installing python-3.7.8"
   assertCaptured "security update!"
@@ -137,10 +129,6 @@ testPython3_7_warn() {
 }
 
 testPython3_8() {
-  # Python 3.7+ requires newer libssl than is present on Cedar-14.
-  if [[ "${STACK}" = "cedar-14" ]]; then
-    return
-  fi
   compile "python3_8"
   assertCaptured "Installing ${LATEST_38}"
   assertNotCaptured "security update"
@@ -150,10 +138,6 @@ testPython3_8() {
 }
 
 testPython3_8_warn() {
-  # Python 3.7+ requires newer libssl than is present on Cedar-14.
-  if [[ "${STACK}" = "cedar-14" ]]; then
-    return
-  fi
   compile "python3_8_warn"
   assertCaptured "Installing python-3.8.5"
   assertCaptured "security update!"
@@ -162,10 +146,6 @@ testPython3_8_warn() {
 }
 
 testPython3_9() {
-  # Cedar-14 is EOL, so we're not building new major Python versions for it.
-  if [[ "${STACK}" = "cedar-14" ]]; then
-    return
-  fi
   compile "python3_9"
   assertCaptured "Installing ${LATEST_39}"
   assertNotCaptured "security update"
@@ -175,10 +155,6 @@ testPython3_9() {
 }
 
 testPython3_9_warn() {
-  # Cedar-14 is EOL, so we're not building new major Python versions for it.
-  if [[ "${STACK}" = "cedar-14" ]]; then
-    return
-  fi
   # Can't test the version warning until there is at least one old version of Python 3.9.
   if [[ "${LATEST_39}" = "python-3.9.0" ]]; then
     return