Fix internals.md

Author: wheeheee

docs/src/internals.md

@@ -2,19 +2,19 @@
 Functions here are not exported.
 
 ```@docs
-DSP.os_fft_complexity
-DSP.os_prepare_conv
-DSP.os_conv_block!
-DSP.os_filter_transform!
+DSP.Convolutions.os_fft_complexity
+DSP.Convolutions.optimalfftfiltlength
+DSP.Convolutions.os_prepare_conv
+DSP.Convolutions.os_conv_block!
+DSP.Convolutions.os_filter_transform!
 DSP.Windows.makewindow
 DSP.Windows.padplot
-DSP._zeropad
-DSP._zeropad!
-DSP._zeropad_keep_offset
+DSP.Convolutions._zeropad
+DSP.Convolutions._zeropad!
+DSP.Convolutions._zeropad_keep_offset
 DSP.Filters._polyprep
 DSP.Filters.freq_eval
 DSP.Filters.build_grid
 DSP.Filters.lagrange_interp
 DSP.Periodograms.coherence_from_cs!
-DSP.optimalfftfiltlength
 ```