Remove CStr::Right

It was only a wrapper around `std::string::substr`. The interface
matches the usecase more. In some places it's better to use
`std::string::ends_with`.

source/ps/CStr.cpp

@@ -293,13 +293,6 @@ CStr CStr::UpperCase() const
 	return newStr;
 }
 
-// Retrieve the substring of the last n characters
-CStr CStr::Right(size_t len) const
-{
-	ENSURE(len <= length());
-	return substr(length()-len, len);
-}
-
 // Retrieve the substring following the last occurrence of Str
 // (or the whole string if it doesn't contain Str)
 CStr CStr::AfterLast(const CStr& str, size_t startPos) const

source/ps/CStr.h

@@ -161,14 +161,6 @@ public:
 	 **/
 	CStr UpperCase() const;
 
-	/**
-	 * Retrieve last n characters of the CStr.
-	 *
-	 * @param size_t len the number of characters to retrieve.
-	 * @return CStr retrieved substring.
-	 **/
-	CStr Right(size_t len) const;
-
 	/**
 	 * Retrieve substring of the CStr after last occurrence of a string.
 	 * Return substring of the CStr after the last occurrence of the search string.

source/ps/scripting/JSInterface_VFS.cpp

@@ -288,7 +288,7 @@ void WriteJSONFile(const Script::Interface& scriptInterface, const std::wstring&
 bool DeleteCampaignSave(const CStrW& filePath)
 {
 	OsPath realPath;
-	if (!filePath.starts_with(L"saves/campaigns/") || filePath.Right(12) != L".0adcampaign")
+	if (!filePath.starts_with(L"saves/campaigns/") || !filePath.ends_with(L".0adcampaign"))
 		return false;
 	if (!VfsFileExists(filePath))
 		return false;