Use a real newline when wrapping quantiles under the title

[uttam12331]

Summary

The wrap_title_quantiles=True option is supposed to place the quantile summary on a separate line below the parameter name (per its docstring). But the title is built with an escaped backslash:

if wrap_title_quantiles:
    title = "{0} =\n{1}".format(titles[i], title)   # "\n" -> literal backslash-n
else:
    title = "{0} = {1}".format(titles[i], title)

In a normal (non-raw) string, "\n" is a literal backslash followed by n, not a newline. So the feature never wraps — it injects the visible characters \n into the title.

Reproduction

import numpy as np, corner
data = np.random.randn(100, 2)
fig = corner.corner(data, labels=["alpha", "beta"], show_titles=True,
                    title_fmt=".2f", wrap_title_quantiles=True)
# title text is e.g.  'alpha =\n${-0.05}_{-0.98}^{+1.06}$'
#   -> the literal two characters "\n", no real line break

Fix

-                        title = "{0} =\n{1}".format(titles[i], title)
+                        title = "{0} =\n{1}".format(titles[i], title)

Tests

Added test_wrap_title_quantiles, which asserts a title contains a real newline when wrap_title_quantiles=True and none when it's False. It fails on the current code (literal \n, no newline character) and passes with the fix.