yaml: make files comply with YAML specification

Signed-off-by: Luís Ferreira <contact@lsferreira.net>

.cirrus.yml

@@ -23,7 +23,7 @@ environment:
   FULL_BUILD: false
 
 # Linux
-task:
+linux_task:
   name: Ubuntu 18.04 $TASK_NAME_SUFFIX
   container:
     image: ubuntu:18.04
@@ -39,7 +39,7 @@ task:
   << : *COMMON_STEPS_TEMPLATE
 
 # Mac
-task:
+mac_task:
   name: macOS 10.15 x64
   osx_instance:
     image: catalina-xcode
@@ -51,7 +51,7 @@ task:
   << : *COMMON_STEPS_TEMPLATE
 
 # FreeBSD
-task:
+freebsd12_task:
   name: FreeBSD 12.2 x64
   freebsd_instance:
     image_family: freebsd-12-2
@@ -64,7 +64,7 @@ task:
   install_bash_and_git_script: pkg install -y bash git
   << : *COMMON_STEPS_TEMPLATE
 
-task:
+freebsd11_task:
   name: FreeBSD 11.4 x64
   freebsd_instance:
     image_family: freebsd-11-4

.codecov.yml

@@ -14,11 +14,11 @@ codecov:
     # Only CircleCi generates coverages files atm.
     # Don't wait for the other CIs
     - circleci.com
-    - !dtest.dlang.io
-    - !auto-tester.puremagic.com
-    - !appveyor.com
-    - !ci.dlang.io
-    - !travis-ci.org
+    - '!dtest.dlang.io'
+    - '!auto-tester.puremagic.com'
+    - '!appveyor.com'
+    - '!ci.dlang.io'
+    - '!travis-ci.org'
 
   # At CircleCi, the PR is merged into `master` before the testsuite is run.
   # This allows CodeCov to adjust the resulting coverage diff, s.t. it matches