Fix change <= to \leq in documentation (#940)

Author: legendre6891

src/weights.jl

@@ -705,8 +705,8 @@ With [`FrequencyWeights`](@ref), the function returns the same result as
 `quantile` for a vector with repeated values. Weights must be integers.
 
 With non `FrequencyWeights`,  denote ``N`` the length of the vector, ``w`` the vector of weights,
-``h = p (\\sum_{i<= N} w_i - w_1) + w_1`` the cumulative weight corresponding to the
-probability ``p`` and ``S_k = \\sum_{i<=k} w_i`` the cumulative weight for each
+``h = p (\\sum_{i \\leq N} w_i - w_1) + w_1`` the cumulative weight corresponding to the
+probability ``p`` and ``S_k = \\sum_{i \\leq k} w_i`` the cumulative weight for each
 observation, define ``v_{k+1}`` the smallest element of `v` such that ``S_{k+1}``
 is strictly superior to ``h``. The weighted ``p`` quantile is given by ``v_k + \\gamma (v_{k+1} - v_k)``
 with  ``\\gamma = (h - S_k)/(S_{k+1} - S_k)``. In particular, when all weights are equal,