TE-2546 Remove obsolete requirements files

requirements/edx-sandbox/local.txt

@@ -1,3 +0,0 @@
-# Placeholder for code which hasn't yet been updated to no longer use this file.
-# The requirements which were here have been moved to shared.in, and are now
-# incorporated into base.txt

requirements/edx-sandbox/post.txt

@@ -1,3 +0,0 @@
-# Placeholder for code which hasn't yet been updated to no longer use this file.
-# The requirements which were here have been moved to shared.in and base.in,
-# and are now incorporated into base.txt

requirements/edx/github.txt

@@ -1,4 +0,0 @@
-# Placeholder for code which hasn't yet been updated to no longer use this file.
-# The requirements which were here have been moved to github.in, and are now
-# incorporated into the appropriate full requirements files (base.txt,
-# testing.txt, etc.)

requirements/edx/local.txt

@@ -1,4 +0,0 @@
-# Placeholder for code which hasn't yet been updated to no longer use this file.
-# The requirements which were here have been moved to local.in, and are now
-# incorporated into the appropriate full requirements files (base.txt,
-# testing.txt, etc.)

requirements/edx/post.txt

@@ -1,4 +0,0 @@
-# Placeholder for code which hasn't yet been updated to no longer use this file.
-# The requirements which were here have been moved to base.in, and are now
-# incorporated into the appropriate full requirements files (base.txt,
-# testing.txt, etc.)

requirements/edx/pre.txt

@@ -1,7 +0,0 @@
-# DON'T JUST ADD NEW DEPENDENCIES!!!
-#
-# If you open a pull request that adds a new dependency, you should notify:
-#   * @edx/ospr - to check licensing
-#   * @edx/devops - to check system requirements
-
-# Empty file left here until all the places that expect it have been updated.