Remove octal escapes from unicode escape handling

Fixes #11673

lib/ansible/parsing/splitter.py

@@ -29,7 +29,6 @@ _ESCAPE_SEQUENCE_RE = re.compile(r'''
     ( \\U{0}           # 8-digit hex escapes
     | \\u{1}           # 4-digit hex escapes
     | \\x{2}           # 2-digit hex escapes
-    | \\[0-7]{{1,3}}   # Octal escapes
     | \\N\{{[^}}]+\}}  # Unicode characters by name
     | \\[\\'"abfnrtv]  # Single-character escapes
     )'''.format(_HEXCHAR*8, _HEXCHAR*4, _HEXCHAR*2), re.UNICODE | re.VERBOSE)