Refines accessibility button in shortcut summary strings

Root cause: we plan to only capitalize the first letter only, it would cause
this sentence has new capitalized issue.

Next: Refines the sentence.

Bug: 148837311
Test: Manual test
Change-Id: I0f6d3d1a3713701b4e2cd09eb49706bbe4604ce9
diff --git a/res/values/strings.xml b/res/values/strings.xml
index 5ab9c33..461e61c 100644
--- a/res/values/strings.xml
+++ b/res/values/strings.xml
@@ -4962,7 +4962,7 @@
     <!-- Title for accessibility shortcut preference for accessibility apps. [CHAR LIMIT=40] -->
     <string name="accessibility_shortcut_title"><xliff:g id="service" example="Select to Speak">%1$s</xliff:g> shortcut</string>
     <!-- Title for software shortcut in accessibility edit shortcut dialog. [CHAR LIMIT=NONE] -->
-    <string name="accessibility_shortcut_edit_summary_software">Accessibility Button</string>
+    <string name="accessibility_shortcut_edit_summary_software">Accessibility button</string>
     <!-- Title for software shortcut in gesture mode in accessibility edit shortcut dialog while using gesture navigation is enabled. [CHAR LIMIT=NONE] -->
     <string name="accessibility_shortcut_edit_dialog_title_software_gesture">Swipe up with 2 fingers</string>
     <!-- Title for software shortcut in gesture mode in accessibility edit shortcut dialog while using gesture navigation and touch exploration are enabled. [CHAR LIMIT=NONE] -->