correct some explanatory comments

pcigale/sed_modules/xray.py

@@ -64,8 +64,8 @@ class Xray(SedModule):
         # Define frequency corresponding to 2 keV in units of Hz.
         self.nu_2keV = c / lam_2keV
 
-        # We define the wavelength range for the non thermal emission
-        # corresponding to 0.08-1200 keV
+        # We define the wavelength grid for the X-ray emission
+        # corresponding to 0.25-1200 keV
         self.wave = np.logspace(-3, 0.7, 1000)
 
         # X-ray emission from galaxies: 1.hot-gas & 2.X-ray binaries