Remove missed lambda from advanced tutorial (#1238)

The lambda used in the `bwa_map` rule was replaced with a named function
in #911, but this single occurrence was missed

docs/tutorial/advanced.rst

@@ -192,7 +192,7 @@ We modify the rule ``bwa_map`` accordingly:
     rule bwa_map:
         input:
             "data/genome.fa",
-            lambda wildcards: config["samples"][wildcards.sample]
+            get_bwa_map_input_fastqs
         output:
             "mapped_reads/{sample}.bam"
         params: