Update minimum Julia version to 1.6

BioSymbols v3 requires Julia 1.6+, so update the "julia" compat entry and
remove unit testing against Julia 1.0.

.github/workflows/UnitTests.yml

@@ -13,7 +13,6 @@ jobs:
       fail-fast: false
       matrix:
         julia-version:
-          - '1.0' # LTS
           - '1.6' # LTS
           - '1'
         julia-arch: [x64, x86]

Project.toml

@@ -23,7 +23,7 @@ BioSequences = "3"
 GenomicFeatures = "2"
 Indexes = "0.1"
 TranscodingStreams = "0.6, 0.7, 0.8, 0.9"
-julia = "1"
+julia = "1.6"
 
 [extras]
 Documenter = "e30172f5-a6a5-5a46-863b-614d45cd2de4"