Fix typo in sign_define arguments

This commit adds the missing character 's' to "LspDiagnosticInformationSign" and "LspDiagnosticHintSign".

Author: kosayoda

README.md

@@ -113,8 +113,8 @@ let g:diagnostic_sign_priority = 20
 ```vim
 call sign_define("LspDiagnosticsErrorSign", {"text" : "E", "texthl" : "LspDiagnosticsError"})
 call sign_define("LspDiagnosticsWarningSign", {"text" : "W", "texthl" : "LspDiagnosticsWarning"})
-call sign_define("LspDiagnosticInformationSign", {"text" : "I", "texthl" : "LspDiagnosticsInformation"})
-call sign_define("LspDiagnosticHintSign", {"text" : "H", "texthl" : "LspDiagnosticsHint"})
+call sign_define("LspDiagnosticsInformationSign", {"text" : "I", "texthl" : "LspDiagnosticsInformation"})
+call sign_define("LspDiagnosticsHintSign", {"text" : "H", "texthl" : "LspDiagnosticsHint"})
 ```
 
 ### Enable/Disable auto popup window