Remove function isCloudUrl()

The function isCloudUrl() was only called in one place, parse_file().
But, isCloudUrl() could only return true if the filename was of the
git-repository kind (url[branch]). In such a case, control flow would
never reach the point where isCloudUrl() is called, since
is_git_repository() returns non-NULL and the function returns early.

Therefore, remove this function. Moreover, adapt the affected if-statement
by replacing "str && !strcmp(str, ...)" with the more concise
"same_string(str, ...)".

Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>

core/qthelperfromc.h

@@ -5,7 +5,6 @@
 bool getProxyString(char **buffer);
 bool canReachCloudServer();
 void updateWindowTitle();
-bool isCloudUrl(const char *filename);
 void subsurface_mkdir(const char *dir);
 char *get_file_name(const char *fileName);
 void copy_image_and_overwrite(const char *cfileName, const char *path, const char *cnewName);