[DevicePage] Add punctuation to "Enable reverse scrolling" strings

Adds missing punctuation to the reverse scrolling setting strings that
were causing i18n issues.

Screenshot (same image):
https://storage.cloud.google.com/chromium-translation-screenshots/f516453a6d7a904e39e84ec3a0aa12b6e0343203

Buganizer bug: https://buganizer.corp.google.com/issues/169863233

Bug: 1132398
Change-Id: I0de91a3ed664bbaab97dd92c9382a1569e113329
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2443212
Commit-Queue: Daniel Classon <dclasson@google.com>
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Cr-Commit-Position: refs/heads/master@{#812958}

chrome/app/os_settings_strings.grdp

@@ -498,7 +498,7 @@
 
   <!-- Device Page (OS Settings) -->
   <message name="IDS_OS_SETTINGS_TOUCHPAD_REVERSE_SCROLL_LABEL">
-    Enable reverse scrolling <ph name="LINK_BEGIN">&lt;a&gt;</ph>Learn more<ph name="LINK_END">&lt;/a&gt;</ph>
+    Enable reverse scrolling. <ph name="LINK_BEGIN">&lt;a&gt;</ph>Learn more<ph name="LINK_END">&lt;/a&gt;</ph>
   </message>
   <message name="IDS_SETTINGS_DEVICE_TITLE" desc="Name of the settings page which displays device and peripheral settings.">
     Device
@@ -1638,7 +1638,7 @@
     Swap primary mouse button
   </message>
   <message name="IDS_SETTINGS_MOUSE_REVERSE_SCROLL_LABEL" desc="In Device Settings, the text next to the checkbox to set reverse scrolling.">
-    Enable reverse scrolling <ph name="LINK_BEGIN">&lt;a&gt;</ph>Learn more<ph name="LINK_END">&lt;/a&gt;</ph>
+    Enable reverse scrolling. <ph name="LINK_BEGIN">&lt;a&gt;</ph>Learn more<ph name="LINK_END">&lt;/a&gt;</ph>
   </message>
   <message name="IDS_SETTINGS_MOUSE_ACCELERATION_LABEL" desc="In Device Settings, the text next to the checkbox to disable mouse acceleration.">
     Enable mouse acceleration

chrome/app/os_settings_strings_grdp/IDS_OS_SETTINGS_TOUCHPAD_REVERSE_SCROLL_LABEL.png.sha1

-d8b70907a64d121e2063d6faf229295b8e56089f
\ No newline at end of file
+f516453a6d7a904e39e84ec3a0aa12b6e0343203
\ No newline at end of file

chrome/app/os_settings_strings_grdp/IDS_SETTINGS_MOUSE_REVERSE_SCROLL_LABEL.png.sha1

-a5951a0be1d8db1eed35d1fc22331b1450bcf4f0
\ No newline at end of file
+f516453a6d7a904e39e84ec3a0aa12b6e0343203
\ No newline at end of file