final a11y issues

topics/visualisation/tutorials/circos/tutorial.md

@@ -382,7 +382,7 @@ The first data track we will configure, will be the structural variants (SVs) us
 SVs are usually described in terms of the SV **breakpoints** (or **junctions**); sets of genomic locations which are separated by a large distance on the reference genome, but have become adjacent in the sample through the occurrence of structural variants. Unfortunately, there is no standard file format for SV data, with different SV callers outputting different formats. Therefore, our first step will be to transform our input dataset to the Circos format for link tracks.
 
 
-**SV File Format:**
+### SV File Format
 
 ```
 #ASSEMBLY_ID	GS000008107-ASM
@@ -402,7 +402,7 @@ SVs are usually described in terms of the SV **breakpoints** (or **junctions**);
 ```
 
 
-**Circos Input Format:**
+### Circos Input Format
 
 ```
 chromosome - start - end - chromosome - start - end