Regression in parsing of `..` operator in nightly

[dpsanders]

Julia 1.12 (correct):

julia> ..(a, b) = (a, b)
.. (generic function with 1 method)

julia> -1e10..2
(-1.0e10, 2)

Julia nightly (incorrect ParseError):

julia> ..(a, b) = (a, b)
.. (generic function with 1 method)

julia> -1e10..2
ERROR: ParseError:
# Error @ REPL[1]:1:2
-1e10..2
#└───┘ ── invalid numeric constant
Stacktrace:
 [1] top-level scope
   @ REPL:1

Discovered by automated testing of interval arithmetic packages and reported here.