MM-21844 Fix toast text glitch on small window widths

[sudheerDev]

Summary

• Use width to determine the text rather than isMobile func

Ticket Link

https://mattermost.atlassian.net/browse/MM-21844

Screenshots

[jgilliam17]

Tested, looks good to merge.

• No glitch, text and toast look good in small window widths, with or without RHS open

[mattermod]

Test server destroyed

[mattermod]

@sudheerDev
Error trying doing the automated Cherry picking. Please do this manually

+++ Updating remotes...
Fetching upstream
Fetching origin
+++ Updating remotes done...
+++ Creating local branch automated-cherry-pick-of-#4724-upstream-release-5.20-1580129702
Branch 'automated-cherry-pick-of-#4724-upstream-release-5.20-1580129702' set up to track remote branch 'release-5.20' from 'upstream'.
+++ Downloading patch to /tmp/4724.patch (in case you need to do this again)

+++ About to attempt cherry pick of PR. To reattempt:
  $ git am -3 /tmp/4724.patch

Applying: MM-21844 Fix toast text glitch on small window widths
Using index info to reconstruct a base tree...
M	components/post_view/post_list_virtualized/post_list_virtualized.jsx
M	components/toast_wrapper/toast_wrapper.jsx
Falling back to patching base and 3-way merge...
Auto-merging components/toast_wrapper/toast_wrapper.jsx
CONFLICT (content): Merge conflict in components/toast_wrapper/toast_wrapper.jsx
Auto-merging components/post_view/post_list_virtualized/post_list_virtualized.jsx
Patch failed at 0001 MM-21844 Fix toast text glitch on small window widths
Use 'git am --show-current-patch' to see the failed patch
When you have resolved this problem, run "git am --continue".
If you prefer to skip this patch, run "git am --skip" instead.
To restore the original branch and stop patching, run "git am --abort".

+++ Conflicts detected:

UU components/toast_wrapper/toast_wrapper.jsx

+++ Aborting in-progress git am.

+++ Returning you to the master branch and cleaning up.