MNT: No longer specify build requirements

meta.yaml

@@ -25,6 +25,8 @@ build:
 
 requirements:
   host:
+    - {{ compiler('cxx') }}
+    - fsl-base >=2007.0
     - fsl-newnifti >=3.0.4
     - fsl-armawrap >=0.4.1
     - fsl-cprob >=2006.0
@@ -32,6 +34,3 @@ requirements:
     - fsl-newimage >=2006.0
     - fsl-utils >=1908.0
     - fsl-znzlib >=2006.0
-  build:
-    - {{ compiler('cxx') }}
-    - fsl-base >=2007.0