String literal search "/foo/bar" causes an error despite "/" not being a regex special character

Created by: slimsag

Parse error at character 14: got TokenLiteral, want separator or EOF

• Doesn't work: /foo/bar
• Doesn't work: repo:foo /foo/bar
• Works: /foo
• Works: foo/bar
• Works: foo/bar/

Workarounds:

• Quote the string literal: https://sourcegraph.sgdev.org/search?q=%22/foo/bar%22
• Escape the forward slashes with backslashes: \/foo\/bar

Reported by a user at 407948923