Remove references to old discussion style files

lms/envs/common.py

@@ -1831,18 +1831,6 @@ PIPELINE['STYLESHEETS'] = {
         ],
         'output_filename': 'css/lms-style-student-notes.css',
     },
-    'style-discussion-main': {
-        'source_filenames': [
-            'css/discussion/lms-discussion-main.css',
-        ],
-        'output_filename': 'css/discussion/lms-discussion-main.css',
-    },
-    'style-discussion-main-rtl': {
-        'source_filenames': [
-            'css/discussion/lms-discussion-main-rtl.css',
-        ],
-        'output_filename': 'css/discussion/lms-discussion-main-rtl.css',
-    },
     'style-inline-discussion': {
         'source_filenames': [
             'css/discussion/inline-discussion.css',

lms/static/sass/discussion/lms-discussion-main-rtl.scss

@@ -1,16 +0,0 @@
-// ------------------------------
-// LMS discussion main styling
-//
-// NOTE: This is the right-to-left (RTL) configured style compile.
-// It should mirror lms-discussion-main w/ the exception of bi-app references.
-
-// Load the RTL version of the edX Pattern Library
-$pattern-library-path: '../../edx-pattern-library' !default;
-
-@import 'edx-pattern-library/pattern-library/sass/edx-pattern-library-rtl';
-
-// Configure RTL variables
-@import 'base/variables-rtl';
-
-// Load the shared build
-@import 'build';

lms/static/sass/discussion/lms-discussion-main.scss

@@ -1,16 +0,0 @@
-// ------------------------------
-// LMS discussion main styling
-//
-// NOTE: This is the left-to-right (LTR) configured style compile.
-// It should mirror lms-discussion-main-rtl w/ the exception of bi-app references.
-
-// Load the LTR version of the edX Pattern Library
-$pattern-library-path: '../../edx-pattern-library' !default;
-
-@import 'edx-pattern-library/pattern-library/sass/edx-pattern-library-ltr';
-
-// Configure LTR variables
-@import 'base/variables-ltr';
-
-// Load the shared build
-@import 'build';