fix: preprocessor indexing error in #elif parsing

Author: AljenU

fortls/parse_fortran.py

@@ -2141,7 +2141,7 @@ def replace_vars(line: str):
                     exc_start = True
                 else:
                     if eval_pp_if(line[match.end(1) :], defs_tmp):
-                        pp_stack[-1][1] = i - 1
+                        pp_stack[-1][1] = i + 1
                         pp_skips.append(pp_stack.pop())
                         pp_stack.append([-1, -1])
                         inc_start = True