docs(builtin): fix some missing lines (#24615)

These two functions seem to have previously had their docs start on the same
line as the signature, which I guess contributed to the lines being lost (though
I checked all other such functions from before again and these were the only
two).

src/nvim/eval.lua

@@ -5057,6 +5057,7 @@ M.funcs = {
     args = 1,
     base = 1,
     desc = [=[
+      The result is a Number, which is indent of line {lnum} in the
       current buffer.  The indent is counted in spaces, the value
       of 'tabstop' is relevant.  {lnum} is used just like in
       |getline()|.
@@ -5775,6 +5776,7 @@ M.funcs = {
     args = 1,
     base = 1,
     desc = [=[
+      The result is a Number, which is the length of the argument.
       When {expr} is a String or a Number the length in bytes is
       used, as with |strlen()|.
       When {expr} is a |List| the number of items in the |List| is